Clean git

Mircea Baja - 7 July 2022

# Clean git

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---
class: large-points

# Agenda

- Strategies
- Tactics
- Tips

- for a cleaner git history **in an imperfect world**

- will use git command line
- your tooling (stash/github/IDE) lies on top of it, principles stay the same

---

# Basics/Prerequisites

---

# Linear local

<pre>repo$ git init
Initialised empty Git repository in repo/.git/
repo (master #%)$ git add a.txt
repo (master +)$ git status
...
 new file: a.txt
...
repo (master +)$ git diff --staged
...
repo (master +)$ git commit -m 'Initial'
[master (root-commit) 902c9e2] Initial
 1 file changed, 5 insertions(+)
 create mode 100644 a.txt
repo (master)$ 
</pre>

---

# Tip #1

<pre>repo (some_branch)$ - branch name
repo (some_branch %)$ - untracked files
repo (some_branch *)$ - modified files
repo (some_branch +)$ - uncommitted files
repo (some_branch=)$ - local in same as remote
repo (some_branch *=)$ - in sync with remote, but modified files
repo (some_branch>)$ - ahead of remote
repo (some_branch<)$ - behind remote
</pre>

```bash
GIT_PS1_SHOWDIRTYSTATE=1
GIT_PS1_SHOWUNTRACKEDFILES=1
GIT_PS1_SHOWSTASHSTATE=1
GIT_PS1_SHOWUPSTREAM="auto"

PS1='...\[\033[01;33m\]$(__git_ps1 " (%s)")\[\033[00m\]\$ '
```

---

# Linear remote

<pre>temp$ git clone repo.git
Cloning into 'repo'...
done.
temp$ cd repo
repo (master=)$ git pull
Already up-to-date.
...
repo (master *=)$ git commit -am 'Change 3'
[master 2180e3e] Change 3
 1 file changed, 1 insertion(+), 1 deletion(-)
repo (master>)$ git log --oneline
* 2180e3e (HEAD -> master) Change 3
* 6c3a5fd (origin/master, origin/HEAD) Change 2
* 34d83e5 Change 1
* 5cbc335 Initial
repo (master>)$ git push
...
 6c3a5fd..2180e3e master -> master
repo (master=)$ 
</pre>

---

# Linear

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 <text class="svg20220701-1-t1" x="350" y="20" fill="#2f332b" text-anchor="middle">master</text>
 <text class="svg20220701-1-t1" x="450" y="106" fill="#2f332b" text-anchor="start">staging/workspace</text>
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- the closer to a linear history, the easier to understand

---

# Branch

<pre>repo (master=)$ git checkout -b some_branch
...
repo (some_branch *)$ git commit -am 'Change 4'
[some_branch c8bb82d] Change 4
 1 file changed, 1 insertion(+), 1 deletion(-)
repo (some_branch)$ git push
fatal: The current branch some_branch has no upstream branch.
...
 git push --set-upstream origin some_branch
repo (some_branch)$ git push --set-upstream origin some_branch
...
repo (some_branch=)$ git checkout -
repo (master=)$ 
</pre>

---

# Tip #2

<pre>
repo (some_branch)$ git push
fatal: The current branch some_branch has no upstream branch.
...
 git push --set-upstream origin some_branch
repo (some_branch)$ git push --set-upstream origin some_branch
repo (some_branch=)$
</pre>
 
<pre>
repo (some_branch)$ git config --global push.default current
</pre>
 
<pre>
repo (some_branch)$ git push -u
repo (some_branch=)$
</pre>

---

# Branch

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- design language used in these diagrams has time flowing left to right

---

# Tip #3

<pre>
repo (some_branch=)$ git log --graph --oneline some_branch master
* 49d5900 (origin/master, origin/HEAD, master) Other change
| * c8bb82d (HEAD -> some_branch, origin/some_branch) Change 4
|/ 
* 2180e3e Change 3
* 6c3a5fd Change 2
* 34d83e5 Change 1
* 5cbc335 Initial
repo (some_branch=)$ 
</pre>
</pre>

- in git log time flows bottom to top

---

# Branching strategies

---

# Git flow

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Vincent Driessen 2010 https://nvie.com/posts/a-successful-git-branching-model/

---

# Trunk based development

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 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 1170 300 L 1230 300"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 1270 300 L 1330 300"/>
 <path stroke-width="4" fill="none" stroke="#8f4300" d="M 1370 300 L 1380 300 Q 1400 300 1400 280 L 1400 160 Q 1400 140 1420 140 L 1430 140"/>
 <circle cx="50" cy="140" r="20" stroke-width="4" stroke="#2f332b" fill="#f5bb00"/>
 <circle cx="150" cy="140" r="20" stroke-width="4" stroke="#2f332b" fill="#f5bb00"/>
 <circle cx="250" cy="140" r="20" stroke-width="4" stroke="#2f332b" fill="#f5bb00"/>
 <circle cx="350" cy="140" r="20" stroke-width="4" stroke="#2f332b" fill="#f5bb00"/>
 <circle cx="450" cy="140" r="20" stroke-width="4" stroke="#2f332b" fill="#ee6055"/>
 <circle cx="450" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#8ea604"/>
 <circle cx="550" cy="140" r="20" stroke-width="4" stroke="#2f332b" fill="#f5bb00"/>
 <circle cx="750" cy="140" r="20" stroke-width="4" stroke="#2f332b" fill="#f5bb00"/>
 <circle cx="850" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#8ea604"/>
 <circle cx="950" cy="140" r="20" stroke-width="4" stroke="#2f332b" fill="#9665ac"/>
 <circle cx="950" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#8ea604"/>
 <circle cx="1050" cy="140" r="20" stroke-width="4" stroke="#2f332b" fill="#9665ac"/>
 <circle cx="1050" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#8ea604"/>
 <circle cx="1150" cy="140" r="20" stroke-width="4" stroke="#2f332b" fill="#9665ac"/>
 <circle cx="1150" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#8ea604"/>
 <circle cx="1350" cy="140" r="20" stroke-width="4" stroke="#2f332b" fill="#f5bb00"/>
 <circle cx="1450" cy="140" r="20" stroke-width="4" stroke="#2f332b" fill="#f5bb00"/>
 <circle cx="1550" cy="140" r="20" stroke-width="4" stroke="#2f332b" fill="#9665ac"/>
 <circle cx="350" cy="220" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="450" cy="220" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="950" cy="220" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="1250" cy="220" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="450" cy="300" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="550" cy="300" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="650" cy="300" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="1150" cy="300" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="1250" cy="300" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="1350" cy="300" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <text class="svg20220701-7-t1" x="1700" y="60" fill="#2f332b" text-anchor="start">release</text>
 <text class="svg20220701-7-t1" x="1700" y="140" fill="#2f332b" text-anchor="start">develop</text>
 <text class="svg20220701-7-t1" x="1700" y="260" fill="#2f332b" text-anchor="start">feature</text>
 <text class="svg20220701-7-t1" x="50" y="100" fill="#2f332b" text-anchor="middle">tag 0.1</text>
 <text class="svg20220701-7-t1" x="450" y="20" fill="#2f332b" text-anchor="middle">tag 0.2</text>
 <text class="svg20220701-7-t1" x="1150" y="20" fill="#2f332b" text-anchor="middle">tag 1.0</text>
 <text class="svg20220701-7-t1" x="1550" y="100" fill="#2f332b" text-anchor="middle">tag 1.1</text>
</svg>
</div>

- Also see Github flow vs. release flow: Edward Thomson 2018 https://www.youtube.com/watch?v=ykZbBD-CmP8

---
class: large-points

# Tip #4

- branch name prefixes indicate the lifetime of the branch
  - "bugfix" means "it goes into release", not "it fixes a bug"
  - "feature" means "it goes into develop", not "it's a feature, not a bug"
  - "release" means "from develop to get release ready"

---
class: large-points

# Tip #5

- use tags for released versions: tags don't move with new commits

- sometimes tags end up on commits on develop (when release needs no other
  changes)
- fix bugs in develop, cherry pick in release (rather than merge): when fixing
  a bug, not known beforehand if it will be needed in a certain release

---
class: large-points
# Tip #6

<div align="center">
<svg xmlns="http://www.w3.org/2000/svg" id="svg20220701-6-1" width="100%" viewBox="0 0 1000 280">
 <style>
 #svg20220701-6-1 {
 border: 1px solid #e8e8e8;
 background-color: #f5f5f5;
 }
 .svg20220701-6-t1 {
 font-family: sans-serif;
 font-size: 16px;
 font-weight: bold;
 dominant-baseline: middle;
 }
 </style>
 <path stroke="none" fill="#ffffff" d="M 0 32 L 772 32 L 800 60 L 772 88 L 0 88 Z"/>
 <path stroke="none" fill="#ffffff" d="M 0 112 L 772 112 L 800 140 L 772 168 L 0 168 Z"/>
 <path stroke="none" fill="#ffffff" d="M 0 192 L 772 192 L 800 220 L 772 248 L 0 248 Z"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 70 60 L 280 60"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 320 60 L 430 60"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 70 60 L 80 60 Q 100 60 100 80 L 100 120 Q 100 140 120 140 L 130 140"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 170 140 L 230 140"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 270 140 L 330 140"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 370 140 L 380 140 Q 400 140 400 120 L 400 80 Q 400 60 420 60 L 430 60"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 370 140 L 430 140"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 70 60 L 80 60 Q 100 60 100 80 L 100 200 Q 100 220 120 220 L 130 220"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 170 220 L 230 220"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 270 220 L 330 220"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 370 220 L 430 220"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 470 220 L 530 220"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 470 60 L 480 60 Q 500 60 500 80 L 500 200 Q 500 220 520 220 L 530 220"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 470 60 L 530 60"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 570 60 L 630 60"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 570 220 L 580 220 Q 600 220 600 200 L 600 80 Q 600 60 620 60 L 630 60"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 570 220 L 630 220"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 670 60 L 680 60 Q 700 60 700 80 L 700 200 Q 700 220 720 220 L 730 220"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 670 220 L 730 220"/>
 <circle cx="50" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#9665ac"/>
 <circle cx="300" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#9665ac"/>
 <circle cx="450" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#9665ac"/>
 <circle cx="150" cy="140" r="20" stroke-width="4" stroke="#2f332b" fill="#2d93ad"/>
 <circle cx="250" cy="140" r="20" stroke-width="4" stroke="#2f332b" fill="#2d93ad"/>
 <circle cx="350" cy="140" r="20" stroke-width="4" stroke="#2f332b" fill="#2d93ad"/>
 <circle cx="450" cy="140" r="20" stroke-width="4" stroke="#2f332b" fill="#2d93ad"/>
 <circle cx="150" cy="220" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="250" cy="220" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="350" cy="220" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="450" cy="220" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="550" cy="220" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="550" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#9665ac"/>
 <circle cx="650" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#9665ac"/>
 <circle cx="650" cy="220" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="750" cy="220" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <text class="svg20220701-6-t1" x="810" y="60" fill="#2f332b" text-anchor="start">master</text>
 <text class="svg20220701-6-t1" x="810" y="140" fill="#2f332b" text-anchor="start">blue_branch</text>
 <text class="svg20220701-6-t1" x="810" y="220" fill="#2f332b" text-anchor="start">pink_branch</text>
</svg>
</div>

- avoid strategies that can involve complex merge conflict resolution
- e.g. long lived interwoven branches

---
class: large-points

# Tip #7

- treat feature and release branches as practically private, short lived
  branches with a single owner

---

# Tip #8: first parent

---

# Uh-oh

<div align="center">
<svg xmlns="http://www.w3.org/2000/svg" id="svg20220701-4-1" width="100%" viewBox="0 0 1800 430">
 <style>
 #svg20220701-4-1 {
 border: 1px solid #e8e8e8;
 background-color: #f5f5f5;
 }
 .svg20220701-4-t1 {
 font-family: sans-serif;
 font-size: 16px;
 font-weight: bold;
 dominant-baseline: middle;
 }
 </style>
 <path stroke="none" fill="#ffffff" d="M 1600 32 L 1672 32 L 1700 60 L 1672 88 L 1600 88 Z"/>
 <path stroke="none" fill="#ffffff" d="M 1600 192 L 1672 192 L 1700 220 L 1672 248 L 1600 248 Z"/>
 <path stroke-width="4" fill="none" stroke="#8f4300" d="M 470 300 L 480 300 Q 500 300 500 320 L 500 360 Q 500 380 520 380 L 530 380"/>
 <path stroke-width="4" fill="none" stroke="#8f4300" d="M 470 300 L 480 300 Q 500 300 500 280 L 500 240 Q 500 220 520 220 L 530 220"/>
 <path stroke-width="4" fill="none" stroke="#8f4300" d="M 970 220 L 980 220 Q 1000 220 1000 200 L 1000 160 Q 1000 140 1020 140 L 1030 140"/>
 <path stroke-width="4" fill="none" stroke="#8f4300" d="M 1170 300 L 1180 300 Q 1200 300 1200 320 L 1200 360 Q 1200 380 1220 380 L 1230 380"/>
 <path stroke-width="4" fill="none" stroke="#8f4300" d="M 1170 300 L 1180 300 Q 1200 300 1200 280 L 1200 240 Q 1200 220 1220 220 L 1230 220"/>
 <path stroke-width="4" fill="none" stroke="#8f4300" d="M 1570 140 L 1580 140 Q 1600 140 1600 160 L 1600 200 Q 1600 220 1620 220 L 1630 220"/>
 <path stroke-width="4" fill="none" stroke="#8f4300" d="M 1570 140 L 1580 140 Q 1600 140 1600 120 L 1600 80 Q 1600 60 1620 60 L 1630 60"/>
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 <path stroke-width="4" fill="none" stroke="#8f4300" d="M 670 140 L 730 140"/>
 <path stroke-width="4" fill="none" stroke="#8f4300" d="M 1370 140 L 1380 140 Q 1400 140 1400 120 L 1400 80 Q 1400 60 1420 60 L 1430 60"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 70 60 L 80 60 Q 100 60 100 80 L 100 360 Q 100 380 120 380 L 530 380"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 70 60 L 80 60 Q 100 60 100 80 L 100 280 Q 100 300 120 300 L 430 300"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 70 60 L 130 60"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 570 380 L 1230 380"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 1270 380 L 1430 380 Q 1450 380 1450 360 L 1450 240 Q 1450 220 1470 220 L 1630 220"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 870 220 L 930 220"/>
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 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 1070 300 L 1130 300"/>
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 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 370 140 L 430 140"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 570 220 L 680 220 Q 700 220 700 200 L 700 160 Q 700 140 720 140 L 730 140"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 770 140 L 780 140 Q 800 140 800 160 L 800 200 Q 800 220 820 220 L 830 220"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 770 140 L 1030 140"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 1070 140 L 1080 140 Q 1100 140 1100 160 L 1100 200 Q 1100 220 1120 220 L 1230 220"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 1070 140 L 1130 140"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 1270 220 L 1280 220 Q 1300 220 1300 200 L 1300 80 Q 1300 60 1320 60 L 1330 60"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 1370 60 L 1430 60"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 1470 60 L 1480 60 Q 1500 60 1500 80 L 1500 120 Q 1500 140 1520 140 L 1530 140"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 1470 60 L 1630 60"/>
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 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 570 140 L 630 140"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 1170 140 L 1230 140"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 1270 140 L 1330 140"/>
 <circle cx="50" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#2d93ad"/>
 <circle cx="550" cy="380" r="20" stroke-width="4" stroke="#2f332b" fill="#2d93ad"/>
 <circle cx="1250" cy="380" r="20" stroke-width="4" stroke="#2f332b" fill="#2d93ad"/>
 <circle cx="1650" cy="220" r="20" stroke-width="4" stroke="#2f332b" fill="#2d93ad"/>
 <circle cx="450" cy="300" r="20" stroke-width="4" stroke="#2f332b" fill="#2d93ad"/>
 <circle cx="850" cy="220" r="20" stroke-width="4" stroke="#2f332b" fill="#2d93ad"/>
 <circle cx="950" cy="220" r="20" stroke-width="4" stroke="#2f332b" fill="#2d93ad"/>
 <circle cx="1050" cy="300" r="20" stroke-width="4" stroke="#2f332b" fill="#2d93ad"/>
 <circle cx="1150" cy="300" r="20" stroke-width="4" stroke="#2f332b" fill="#2d93ad"/>
 <circle cx="1550" cy="140" r="20" stroke-width="4" stroke="#2f332b" fill="#2d93ad"/>
 <circle cx="1050" cy="220" r="20" stroke-width="4" stroke="#2f332b" fill="#2d93ad"/>
 <circle cx="150" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#2d93ad"/>
 <circle cx="250" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#2d93ad"/>
 <circle cx="350" cy="140" r="20" stroke-width="4" stroke="#2f332b" fill="#2d93ad"/>
 <circle cx="550" cy="220" r="20" stroke-width="4" stroke="#2f332b" fill="#2d93ad"/>
 <circle cx="750" cy="140" r="20" stroke-width="4" stroke="#2f332b" fill="#2d93ad"/>
 <circle cx="1050" cy="140" r="20" stroke-width="4" stroke="#2f332b" fill="#2d93ad"/>
 <circle cx="1250" cy="220" r="20" stroke-width="4" stroke="#2f332b" fill="#2d93ad"/>
 <circle cx="1350" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#2d93ad"/>
 <circle cx="1450" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#2d93ad"/>
 <circle cx="1650" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#ffffff"/>
 <circle cx="350" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#2d93ad"/>
 <circle cx="450" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#2d93ad"/>
 <circle cx="950" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#2d93ad"/>
 <circle cx="1250" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#2d93ad"/>
 <circle cx="450" cy="140" r="20" stroke-width="4" stroke="#2f332b" fill="#2d93ad"/>
 <circle cx="550" cy="140" r="20" stroke-width="4" stroke="#2f332b" fill="#2d93ad"/>
 <circle cx="650" cy="140" r="20" stroke-width="4" stroke="#2f332b" fill="#2d93ad"/>
 <circle cx="1150" cy="140" r="20" stroke-width="4" stroke="#2f332b" fill="#2d93ad"/>
 <circle cx="1250" cy="140" r="20" stroke-width="4" stroke="#2f332b" fill="#2d93ad"/>
 <circle cx="1350" cy="140" r="20" stroke-width="4" stroke="#2f332b" fill="#2d93ad"/>
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 <text class="svg20220701-4-t1" x="1700" y="60" fill="#2f332b" text-anchor="start">develop</text>
 <text class="svg20220701-4-t1" x="50" y="20" fill="#2f332b" text-anchor="middle">tag 0.1</text>
 <text class="svg20220701-4-t1" x="550" y="340" fill="#2f332b" text-anchor="middle">tag 0.2</text>
 <text class="svg20220701-4-t1" x="1250" y="340" fill="#2f332b" text-anchor="middle">tag 1.0</text>
 <text class="svg20220701-4-t1" x="1650" y="180" fill="#2f332b" text-anchor="middle">tag 1.1</text>
</svg>
</div>

- a branch is not a sequence of commits, it just points to a commit

---

# Uh-oh

<div align="center">
<svg xmlns="http://www.w3.org/2000/svg" id="svg20220701-5-1" width="100%" viewBox="0 0 1800 430">
 <style>
 #svg20220701-5-1 {
 border: 1px solid #e8e8e8;
 background-color: #f5f5f5;
 }
 .svg20220701-5-t1 {
 font-family: sans-serif;
 font-size: 16px;
 font-weight: bold;
 dominant-baseline: middle;
 }
 </style>
 <path stroke="none" fill="#ffffff" d="M 1600 32 L 1672 32 L 1700 60 L 1672 88 L 1600 88 Z"/>
 <path stroke="none" fill="#ffffff" d="M 1600 192 L 1672 192 L 1700 220 L 1672 248 L 1600 248 Z"/>
 <path stroke-width="4" fill="none" stroke="#8f4300" d="M 470 300 L 480 300 Q 500 300 500 320 L 500 360 Q 500 380 520 380 L 530 380"/>
 <path stroke-width="4" fill="none" stroke="#8f4300" d="M 470 300 L 480 300 Q 500 300 500 280 L 500 240 Q 500 220 520 220 L 530 220"/>
 <path stroke-width="4" fill="none" stroke="#8f4300" d="M 970 220 L 980 220 Q 1000 220 1000 200 L 1000 160 Q 1000 140 1020 140 L 1030 140"/>
 <path stroke-width="4" fill="none" stroke="#8f4300" d="M 1170 300 L 1180 300 Q 1200 300 1200 320 L 1200 360 Q 1200 380 1220 380 L 1230 380"/>
 <path stroke-width="4" fill="none" stroke="#8f4300" d="M 1170 300 L 1180 300 Q 1200 300 1200 280 L 1200 240 Q 1200 220 1220 220 L 1230 220"/>
 <path stroke-width="4" fill="none" stroke="#8f4300" d="M 1570 140 L 1580 140 Q 1600 140 1600 160 L 1600 200 Q 1600 220 1620 220 L 1630 220"/>
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 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 1070 300 L 1130 300"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 970 220 L 1030 220"/>
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 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 270 60 L 280 60 Q 300 60 300 80 L 300 120 Q 300 140 320 140 L 330 140"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 270 60 L 330 60"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 370 140 L 380 140 Q 400 140 400 160 L 400 200 Q 400 220 420 220 L 530 220"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 370 140 L 430 140"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 570 220 L 680 220 Q 700 220 700 200 L 700 160 Q 700 140 720 140 L 730 140"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 770 140 L 780 140 Q 800 140 800 160 L 800 200 Q 800 220 820 220 L 830 220"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 770 140 L 1030 140"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 1070 140 L 1080 140 Q 1100 140 1100 160 L 1100 200 Q 1100 220 1120 220 L 1230 220"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 1070 140 L 1130 140"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 1270 220 L 1280 220 Q 1300 220 1300 200 L 1300 80 Q 1300 60 1320 60 L 1330 60"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 1370 60 L 1430 60"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 1470 60 L 1480 60 Q 1500 60 1500 80 L 1500 120 Q 1500 140 1520 140 L 1530 140"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 1470 60 L 1630 60"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 370 60 L 430 60"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 470 60 L 930 60"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 970 60 L 1230 60"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 470 140 L 530 140"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 570 140 L 630 140"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 1170 140 L 1230 140"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 1270 140 L 1330 140"/>
 <circle cx="50" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#2d93ad"/>
 <circle cx="550" cy="380" r="20" stroke-width="4" stroke="#2f332b" fill="#2d93ad"/>
 <circle cx="1250" cy="380" r="20" stroke-width="4" stroke="#2f332b" fill="#2d93ad"/>
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 <circle cx="450" cy="300" r="20" stroke-width="4" stroke="#2f332b" fill="#ee6055"/>
 <circle cx="850" cy="220" r="20" stroke-width="4" stroke="#2f332b" fill="#8ea604"/>
 <circle cx="950" cy="220" r="20" stroke-width="4" stroke="#2f332b" fill="#8ea604"/>
 <circle cx="1050" cy="300" r="20" stroke-width="4" stroke="#2f332b" fill="#8ea604"/>
 <circle cx="1150" cy="300" r="20" stroke-width="4" stroke="#2f332b" fill="#8ea604"/>
 <circle cx="1550" cy="140" r="20" stroke-width="4" stroke="#2f332b" fill="#8ea604"/>
 <circle cx="1050" cy="220" r="20" stroke-width="4" stroke="#2f332b" fill="#9665ac"/>
 <circle cx="150" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#f5bb00"/>
 <circle cx="250" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#f5bb00"/>
 <circle cx="350" cy="140" r="20" stroke-width="4" stroke="#2f332b" fill="#f5bb00"/>
 <circle cx="550" cy="220" r="20" stroke-width="4" stroke="#2f332b" fill="#f5bb00"/>
 <circle cx="750" cy="140" r="20" stroke-width="4" stroke="#2f332b" fill="#f5bb00"/>
 <circle cx="1050" cy="140" r="20" stroke-width="4" stroke="#2f332b" fill="#f5bb00"/>
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 <circle cx="1350" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#f5bb00"/>
 <circle cx="1450" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#f5bb00"/>
 <circle cx="1650" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#f5bb00"/>
 <circle cx="350" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="450" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="950" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="1250" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="450" cy="140" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="550" cy="140" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="650" cy="140" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="1150" cy="140" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="1250" cy="140" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="1350" cy="140" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <text class="svg20220701-5-t1" x="1700" y="220" fill="#2f332b" text-anchor="start">master</text>
 <text class="svg20220701-5-t1" x="1700" y="60" fill="#2f332b" text-anchor="start">develop</text>
 <text class="svg20220701-5-t1" x="50" y="20" fill="#2f332b" text-anchor="middle">tag 0.1</text>
 <text class="svg20220701-5-t1" x="550" y="340" fill="#2f332b" text-anchor="middle">tag 0.2</text>
 <text class="svg20220701-5-t1" x="1250" y="340" fill="#2f332b" text-anchor="middle">tag 1.0</text>
 <text class="svg20220701-5-t1" x="1650" y="180" fill="#2f332b" text-anchor="middle">tag 1.1</text>
</svg>
</div>

---

# Log

<pre>repo (develop=)$ git log --oneline develop
a5d20f6 (HEAD -> develop, origin/develop) Merge branch 'release2' into develop
1f97e98 Merge branch 'feature6' into develop
c185f20 Merge branch 'bugfix6' into release2
8602ef3 Merge branch 'feature3' into develop
1c42702 Change 18
4bf0480 Change 19
c911945 Merge branch 'release1' into develop
3a506a2 Change 17
c340264 Change 16
640661e Merge branch 'release1' into develop
</pre>

- ordered by commit date which is useless in a complex repository

---

# Log graph

<pre>repo (develop=)$ git log --graph --oneline develop
* a5d20f6 (HEAD -> develop, origin/develop) Merge branch 'release2' into develop
|\ 
| * c185f20 Merge branch 'bugfix6' into release2
|/| 
| * 4bf0480 Change 19
|/ 
* 1f97e98 Merge branch 'feature6' into develop
|\ 
| * 1c42702 Change 18
| * c340264 Change 16
* | 8602ef3 Merge branch 'feature3' into develop
|\ \ 
| * | 3a506a2 Change 17
| * | efa40dc Change 13
| * | c8d7baa Change 4
* | | c911945 Merge branch 'release1' into develop
|\ \ \ 
</pre>

- first parent always on the left

---

# Commit parents

<pre>repo (develop=)$ git show a5d20f6
commit a5d20f6726de26a42b58223f2feb45ec04c1afd8 (HEAD -> develop, origin/develop)
Merge: 1f97e98 c185f20
Author: Alice <alice@example.com>
Date: Tue Jun 28 21:16:53 2022 +0100

Merge branch 'release2' into develop
repo (develop=)$ 
</pre>

---

# Log first parent

<pre>repo (develop=)$ git log --first-parent --graph --oneline develop
* a5d20f6 (HEAD -> develop, origin/develop) Merge branch 'release2' into develop
* 1f97e98 Merge branch 'feature6' into develop
* 8602ef3 Merge branch 'feature3' into develop
* c911945 Merge branch 'release1' into develop
...
* d8784d8 (tag: 0.1) Change 1
</pre>

- this logs develop
- if first parent is correct
- though eventually it follows master

---

# Log commits from branch

<pre>repo (develop=)$ git log --oneline --graph --parents develop
* a5d20f6 1f97e98 c185f20 (HEAD -> develop, origin/develop) Merge branch 'release2' into develop
|\ 
| * c185f20 1f97e98 4bf0480 Merge branch 'bugfix6' into release2
|/| 
| * 4bf0480 1f97e98 Change 19
|/ 
* 1f97e98 8602ef3 1c42702 Merge branch 'feature6' into develop
|\ 
...
repo (develop=)$ git log --oneline --graph --parents ^1f97e98 c185f20
* c185f20 1f97e98 4bf0480 Merge branch 'bugfix6' into release2
* 4bf0480 1f97e98 Change 19
repo (develop=)$ 
</pre>

- caret prefix means "not in this commit"

---

# Caret and tilde suffixes

- caret suffix follows breadth, tilde follows depth

<pre>a5d20f6^ is 1f97e98
a5d20f6~ is 1f97e98
a5d20f6^2 is c185f20
a5d20f6~2 is 1f97e98~ which is 8602ef3
a5d20f6^^ is 1f97e98^ which is 8602ef3
a5d20f6^2^ is c185f20^ which is 1f97e98
</pre>

---

# Tactics

---

# Merge commit

<div align="center">
<svg xmlns="http://www.w3.org/2000/svg" id="svg20220701-8-1" width="100%" viewBox="0 0 1200 200">
 <style>
 #svg20220701-8-1 {
 border: 1px solid #e8e8e8;
 background-color: #f5f5f5;
 }
 .svg20220701-8-t1 {
 font-family: sans-serif;
 font-size: 16px;
 font-weight: bold;
 dominant-baseline: middle;
 }
 </style>
 <path stroke="none" fill="#ffffff" d="M 0 32 L 322 32 L 350 60 L 322 88 L 0 88 Z"/>
 <path stroke="none" fill="#ffffff" d="M 50 132 L 372 132 L 400 160 L 372 188 L 50 188 Z"/>
 <path stroke="none" fill="#ffffff" d="M 600 32 L 1072 32 L 1100 60 L 1072 88 L 600 88 Z"/>
 <path stroke="none" fill="#ffffff" d="M 650 132 L 1050 132 L 1050 188 L 650 188 Z"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 70 60 L 280 60"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 70 60 L 80 60 Q 100 60 100 80 L 100 140 Q 100 160 120 160 L 130 160"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 170 160 L 230 160"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 270 160 L 330 160"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 670 60 L 880 60"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 670 60 L 680 60 Q 700 60 700 80 L 700 140 Q 700 160 720 160 L 730 160"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 770 160 L 830 160"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 870 160 L 930 160"/>
 <path stroke-width="4" fill="none" stroke="#8f4300" d="M 970 160 L 980 160 Q 1000 160 1000 140 L 1000 80 Q 1000 60 1020 60 L 1030 60"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 920 60 L 1030 60"/>
 <circle cx="50" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#f5bb00"/>
 <circle cx="300" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#f5bb00"/>
 <circle cx="150" cy="160" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="250" cy="160" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="350" cy="160" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="650" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#f5bb00"/>
 <circle cx="900" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#f5bb00"/>
 <circle cx="750" cy="160" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="850" cy="160" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="950" cy="160" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="1050" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#f5bb00"/>
 <text class="svg20220701-8-t1" x="300" y="20" fill="#2f332b" text-anchor="middle">develop</text>
 <text class="svg20220701-8-t1" x="350" y="120" fill="#2f332b" text-anchor="middle">feature</text>
 <text class="svg20220701-8-t1" x="1050" y="20" fill="#2f332b" text-anchor="middle">develop</text>
 <text class="svg20220701-8-t1" x="950" y="120" fill="#2f332b" text-anchor="middle">feature</text>
</svg>
</div>

---

# Merge commit

---

# Merge commit

<pre>repo (develop)$ git merge --no-ff feature
</pre>

<pre style="background-color:#eee">Merge branch 'feature' into develop
# Please enter a commit message to explain why this merge is necessary,
...
~ 
:x
</pre>

<pre> Merge made by the 'recursive' strategy.
 a.txt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
repo (develop)$ 
</pre>

---

# Merge commit

<pre>repo (develop)$ git log --oneline --graph develop feature
* 3c37e6d (HEAD -> develop) Merge branch 'feature' into develop
|\ 
| * d0c3ef9 (feature) Change 3
| * 68cdd49 Change 2
| * a6da8b9 Change 1
* | d682b2a Some other change
|/ 
* 34d4b9f Base
repo (develop)$ git show
commit 3c37e6d716f76bb4f4ad2632feb0534be6102481 (HEAD -> develop)
Merge: d682b2a d0c3ef9
Author: Alice <alice@example.com>
Date: Mon Jun 20 21:03:32 2022 +0100

Merge branch 'feature' into develop
repo (develop)$ 
</pre>

---
class: large-points

# Tip #9

- the merge commit can still be semantically wrong
- i.e. parents compile, but the merge does not
- e.g. if one parent removes the definition and usages of a function, but the
  other parent adds one more usage

---

# Fast forward

<div align="center">
<svg xmlns="http://www.w3.org/2000/svg" id="svg20220701-9-1" width="100%" viewBox="0 0 1200 200">
 <style>
 #svg20220701-9-1 {
 border: 1px solid #e8e8e8;
 background-color: #f5f5f5;
 }
 .svg20220701-9-t1 {
 font-family: sans-serif;
 font-size: 16px;
 font-weight: bold;
 dominant-baseline: middle;
 }
 </style>
 <path stroke="none" fill="#ffffff" d="M 0 32 L 122 32 L 150 60 L 122 88 L 0 88 Z"/>
 <path stroke="none" fill="#ffffff" d="M 50 132 L 172 132 L 200 160 L 172 188 L 50 188 Z"/>
 <path stroke="none" fill="#ffffff" d="M 600 32 L 772 32 L 800 60 L 772 88 L 600 88 Z"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 70 60 L 80 60 Q 100 60 100 80 L 100 140 Q 100 160 120 160 L 130 160"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 670 60 L 730 60"/>
 <circle cx="50" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#f5bb00"/>
 <circle cx="150" cy="160" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="650" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#f5bb00"/>
 <circle cx="750" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <text class="svg20220701-9-t1" x="50" y="20" fill="#2f332b" text-anchor="middle">develop</text>
 <text class="svg20220701-9-t1" x="150" y="120" fill="#2f332b" text-anchor="middle">feature</text>
 <text class="svg20220701-9-t1" x="750" y="20" fill="#2f332b" text-anchor="start">develop, feature</text>
</svg>
</div>

---

# Fast forward

<pre>repo (develop)$ git log --oneline --graph develop feature
* d594416 (feature) Change 1
* 364ef22 (HEAD -> develop) Base
repo (develop)$ git merge --ff-only feature
Updating 364ef22..d594416
Fast-forward
 a.txt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
repo (develop)$ git log --oneline --graph develop feature
* d594416 (HEAD -> develop, feature) Change 1
* 364ef22 Base
repo (develop)$ </pre>

---

# Just merge

<pre>
repo (develop)$ git merge feature
</pre>

- fast forward if possible, else create merge commit

---

# Squash merge

<div align="center">
<svg xmlns="http://www.w3.org/2000/svg" id="svg20220701-10-1" width="100%" viewBox="0 0 1200 200">
 <style>
 #svg20220701-10-1 {
 border: 1px solid #e8e8e8;
 background-color: #f5f5f5;
 }
 .svg20220701-10-t1 {
 font-family: sans-serif;
 font-size: 16px;
 font-weight: bold;
 dominant-baseline: middle;
 }
 </style>
 <path stroke="none" fill="#ffffff" d="M 0 32 L 322 32 L 350 60 L 322 88 L 0 88 Z"/>
 <path stroke="none" fill="#ffffff" d="M 50 132 L 372 132 L 400 160 L 372 188 L 50 188 Z"/>
 <path stroke="none" fill="#ffffff" d="M 600 32 L 1022 32 L 1050 60 L 1022 88 L 600 88 Z"/>
 <path stroke="none" fill="#ffffff" d="M 650 132 L 1000 132 L 1000 188 L 650 188 Z"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 70 60 L 280 60"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 70 60 L 80 60 Q 100 60 100 80 L 100 140 Q 100 160 120 160 L 130 160"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 170 160 L 230 160"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 270 160 L 330 160"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 670 60 L 880 60"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 920 60 L 980 60"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 670 60 L 680 60 Q 700 60 700 80 L 700 140 Q 700 160 720 160 L 730 160"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 770 160 L 830 160"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 870 160 L 930 160"/>
 <circle cx="50" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#f5bb00"/>
 <circle cx="300" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#f5bb00"/>
 <circle cx="150" cy="160" r="20" stroke-width="4" stroke="#2f332b" fill="#ffcdea"/>
 <circle cx="250" cy="160" r="20" stroke-width="4" stroke="#2f332b" fill="#ff9bd5"/>
 <circle cx="350" cy="160" r="20" stroke-width="4" stroke="#2f332b" fill="#ff69c0"/>
 <circle cx="650" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#f5bb00"/>
 <circle cx="900" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#f5bb00"/>
 <circle cx="1000" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="750" cy="160" r="20" stroke-width="4" stroke="#2f332b" fill="#ffcdea"/>
 <circle cx="850" cy="160" r="20" stroke-width="4" stroke="#2f332b" fill="#ff9bd5"/>
 <circle cx="950" cy="160" r="20" stroke-width="4" stroke="#2f332b" fill="#ff69c0"/>
 <text class="svg20220701-10-t1" x="300" y="20" fill="#2f332b" text-anchor="middle">develop</text>
 <text class="svg20220701-10-t1" x="350" y="120" fill="#2f332b" text-anchor="middle">feature</text>
 <text class="svg20220701-10-t1" x="1000" y="20" fill="#2f332b" text-anchor="middle">develop</text>
 <text class="svg20220701-10-t1" x="950" y="120" fill="#2f332b" text-anchor="middle">feature</text>
</svg>
</div>

---

# Squash merge

<pre>repo (develop)$ git merge --squash feature
Squash commit -- not updating HEAD
Automatic merge went well; stopped before committing as requested
repo (develop +)$ git commit -m 'Change 1 to 3'
[develop 3c58559] Change 1 to 3
 1 file changed, 1 insertion(+), 1 deletion(-)
repo (develop)$ git log --oneline --graph develop feature
* 3c58559 (HEAD -> develop) Change 1 to 3
* 1678d67 Some other change
| * 4450028 (feature) Change 3
| * 2df5e28 Change 2
| * e27fb78 Change 1
|/ 
* 70045eb Base
repo (develop)$ 
</pre>

---

# Rebase

<div align="center">
<svg xmlns="http://www.w3.org/2000/svg" id="svg20220701-11-1" width="100%" viewBox="0 0 1200 200">
 <style>
 #svg20220701-11-1 {
 border: 1px solid #e8e8e8;
 background-color: #f5f5f5;
 }
 .svg20220701-11-t1 {
 font-family: sans-serif;
 font-size: 16px;
 font-weight: bold;
 dominant-baseline: middle;
 }
 </style>
 <path stroke="none" fill="#ffffff" d="M 0 32 L 172 32 L 200 60 L 172 88 L 0 88 Z"/>
 <path stroke="none" fill="#ffffff" d="M 50 132 L 372 132 L 400 160 L 372 188 L 50 188 Z"/>
 <path stroke="none" fill="#ffffff" d="M 600 32 L 772 32 L 800 60 L 772 88 L 600 88 Z"/>
 <path stroke="none" fill="#ffffff" d="M 750 132 L 1072 132 L 1100 160 L 1072 188 L 750 188 Z"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 70 60 L 130 60"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 70 60 L 80 60 Q 100 60 100 80 L 100 140 Q 100 160 120 160 L 130 160"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 170 160 L 230 160"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 270 160 L 330 160"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 670 60 L 730 60"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 770 60 L 780 60 Q 800 60 800 80 L 800 140 Q 800 160 820 160 L 830 160"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 870 160 L 930 160"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 970 160 L 1030 160"/>
 <circle cx="50" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#f5bb00"/>
 <circle cx="150" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#f5bb00"/>
 <circle cx="150" cy="160" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="250" cy="160" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="350" cy="160" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="650" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#f5bb00"/>
 <circle cx="750" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#f5bb00"/>
 <circle cx="850" cy="160" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="950" cy="160" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="1050" cy="160" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <text class="svg20220701-11-t1" x="150" y="20" fill="#2f332b" text-anchor="middle">develop</text>
 <text class="svg20220701-11-t1" x="350" y="120" fill="#2f332b" text-anchor="middle">feature</text>
 <text class="svg20220701-11-t1" x="750" y="20" fill="#2f332b" text-anchor="middle">develop</text>
 <text class="svg20220701-11-t1" x="1050" y="120" fill="#2f332b" text-anchor="middle">feature</text>
</svg>
</div>

---

# Rebase

<pre>repo (feature)$ git rebase develop
First, rewinding head to replay your work on top of it...
Applying: Change 1
Applying: Change 2
Applying: Change 3
repo (feature)$ git log --oneline --graph develop feature
* c659a53 (HEAD -> feature) Change 3
* 012859d Change 2
* 8dd3340 Change 1
* 4b96ca3 (develop) Some other change
* ce88a4f Base
repo (feature)$ 
</pre>

---

# Interactive rebase

<div align="center">
<svg xmlns="http://www.w3.org/2000/svg" id="svg20220701-12-1" width="100%" viewBox="0 0 1200 200">
 <style>
 #svg20220701-12-1 {
 border: 1px solid #e8e8e8;
 background-color: #f5f5f5;
 }
 .svg20220701-12-t1 {
 font-family: sans-serif;
 font-size: 16px;
 font-weight: bold;
 dominant-baseline: middle;
 }
 </style>
 <path stroke="none" fill="#ffffff" d="M 0 32 L 172 32 L 200 60 L 172 88 L 0 88 Z"/>
 <path stroke="none" fill="#ffffff" d="M 50 132 L 472 132 L 500 160 L 472 188 L 50 188 Z"/>
 <path stroke="none" fill="#ffffff" d="M 600 32 L 772 32 L 800 60 L 772 88 L 600 88 Z"/>
 <path stroke="none" fill="#ffffff" d="M 650 132 L 872 132 L 900 160 L 872 188 L 650 188 Z"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 70 60 L 130 60"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 70 60 L 80 60 Q 100 60 100 80 L 100 140 Q 100 160 120 160 L 130 160"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 170 160 L 230 160"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 270 160 L 330 160"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 370 160 L 430 160"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 670 60 L 730 60"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 670 60 L 680 60 Q 700 60 700 80 L 700 140 Q 700 160 720 160 L 730 160"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 770 160 L 830 160"/>
 <circle cx="50" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#f5bb00"/>
 <circle cx="150" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#f5bb00"/>
 <circle cx="150" cy="160" r="20" stroke-width="4" stroke="#2f332b" fill="#6ac3d9"/>
 <circle cx="250" cy="160" r="20" stroke-width="4" stroke="#2f332b" fill="#ffcdea"/>
 <circle cx="350" cy="160" r="20" stroke-width="4" stroke="#2f332b" fill="#ff9bd5"/>
 <circle cx="450" cy="160" r="20" stroke-width="4" stroke="#2f332b" fill="#6ac3d9"/>
 <circle cx="650" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#f5bb00"/>
 <circle cx="750" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#f5bb00"/>
 <circle cx="750" cy="160" r="20" stroke-width="4" stroke="#2f332b" fill="#2d93ad"/>
 <circle cx="850" cy="160" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <text class="svg20220701-12-t1" x="150" y="20" fill="#2f332b" text-anchor="middle">develop</text>
 <text class="svg20220701-12-t1" x="450" y="120" fill="#2f332b" text-anchor="middle">feature</text>
 <text class="svg20220701-12-t1" x="750" y="20" fill="#2f332b" text-anchor="middle">develop</text>
 <text class="svg20220701-12-t1" x="850" y="120" fill="#2f332b" text-anchor="middle">feature</text>
</svg>
</div>

---

# Interactive rebase

<pre>repo (feature)$ git rebase -i HEAD~4
</pre>

<pre style="background-color:#eee">pick 18dedc5 Change 1
fixup f619bd2 Change 4
pick ec47071 Change 2
fixup 56ce00b Change 3

# Rebase 3d89342..f619bd2 onto f619bd2 (4 commands)
#
# Commands:
# p, pick <commit> = use commit
...
# f, fixup <commit> = like "squash", but discard this commit's log message
...
jjjddkkP
cwfixup ESC
jj0.
:x
</pre>

---

# Interactive rebase

<pre>repo (feature)$ git rebase -i HEAD~4
Successfully rebased and updated refs/heads/feature.
repo (feature)$ git log --oneline --graph develop feature
* 5ca72ab (HEAD -> feature) Change 2
* a9cecf4 Change 1
| * 85b3097 (develop) Some other change
|/ 
* 3d89342 Base
repo (feature)$ 
</pre>

- common to interactive rebase with branch name, e.g. develop, or tilde, e.g. HEAD~4

- when using the `edit` action `git reset HEAD^` is useful

---
class: large-points
# Tip #10

- you don't re-write history: you write a new one

---

# Cherry pick

<div align="center">
<svg xmlns="http://www.w3.org/2000/svg" id="svg20220701-13-1" width="100%" viewBox="0 0 1200 200">
 <style>
 #svg20220701-13-1 {
 border: 1px solid #e8e8e8;
 background-color: #f5f5f5;
 }
 .svg20220701-13-t1 {
 font-family: sans-serif;
 font-size: 16px;
 font-weight: bold;
 dominant-baseline: middle;
 }
 </style>
 <path stroke="none" fill="#ffffff" d="M 50 32 L 172 32 L 200 60 L 172 88 L 50 88 Z"/>
 <path stroke="none" fill="#ffffff" d="M 0 132 L 372 132 L 400 160 L 372 188 L 0 188 Z"/>
 <path stroke="none" fill="#ffffff" d="M 650 32 L 872 32 L 900 60 L 872 88 L 650 88 Z"/>
 <path stroke="none" fill="#ffffff" d="M 600 132 L 972 132 L 1000 160 L 972 188 L 600 188 Z"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 70 160 L 130 160"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 70 160 L 80 160 Q 100 160 100 140 L 100 80 Q 100 60 120 60 L 130 60"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 170 160 L 230 160"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 270 160 L 330 160"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 670 160 L 730 160"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 670 160 L 680 160 Q 700 160 700 140 L 700 80 Q 700 60 720 60 L 730 60"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 770 160 L 830 160"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 870 160 L 930 160"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 770 60 L 830 60"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 870 160 L 830 160 Q 850 160 850 140 L 850 80 Q 850 60 870 60 L 830 60" stroke-dasharray="5, 5"/>
 <circle cx="50" cy="160" r="20" stroke-width="4" stroke="#2f332b" fill="#f5bb00"/>
 <circle cx="150" cy="160" r="20" stroke-width="4" stroke="#2f332b" fill="#f5bb00"/>
 <circle cx="250" cy="160" r="20" stroke-width="4" stroke="#2f332b" fill="#9665ac"/>
 <circle cx="350" cy="160" r="20" stroke-width="4" stroke="#2f332b" fill="#f5bb00"/>
 <circle cx="150" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#8ea604"/>
 <circle cx="650" cy="160" r="20" stroke-width="4" stroke="#2f332b" fill="#f5bb00"/>
 <circle cx="750" cy="160" r="20" stroke-width="4" stroke="#2f332b" fill="#f5bb00"/>
 <circle cx="850" cy="160" r="20" stroke-width="4" stroke="#2f332b" fill="#9665ac"/>
 <circle cx="950" cy="160" r="20" stroke-width="4" stroke="#2f332b" fill="#f5bb00"/>
 <circle cx="750" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#8ea604"/>
 <circle cx="850" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#8ea604"/>
 <text class="svg20220701-13-t1" x="150" y="20" fill="#2f332b" text-anchor="middle">release</text>
 <text class="svg20220701-13-t1" x="350" y="120" fill="#2f332b" text-anchor="middle">develop</text>
 <text class="svg20220701-13-t1" x="850" y="20" fill="#2f332b" text-anchor="middle">release</text>
 <text class="svg20220701-13-t1" x="950" y="120" fill="#2f332b" text-anchor="middle">develop</text>
</svg>
</div>

---

# Cherry pick

<pre>repo (release)$ git log --oneline --graph develop release
* d641e3b (develop) Change 3
* a543eee Bugfix
* af606c4 Change 1
| * 595643f (HEAD -> release) Release change
|/ 
* ec4d982 Base
repo (release)$ git cherry-pick a543eee
[release 567fcc3] Bugfix
...
repo (release)$ git log --oneline --graph develop release
* 567fcc3 (HEAD -> release) Bugfix
* 595643f Release change
| * d641e3b (develop) Change 3
| * a543eee Bugfix
| * af606c4 Change 1
|/ 
* ec4d982 Base
repo (release)$ 
</pre>

---

# Amend

<div align="center">
<svg xmlns="http://www.w3.org/2000/svg" id="svg20220701-14-1" width="100%" viewBox="0 0 1200 200">
 <style>
 #svg20220701-14-1 {
 border: 1px solid #e8e8e8;
 background-color: #f5f5f5;
 }
 .svg20220701-14-t1 {
 font-family: sans-serif;
 font-size: 16px;
 font-weight: bold;
 dominant-baseline: middle;
 }
 </style>
 <path stroke="none" fill="#ffffff" d="M 0 32 L 172 32 L 200 60 L 172 88 L 0 88 Z"/>
 <path stroke="none" fill="#ffffff" d="M 600 32 L 772 32 L 800 60 L 772 88 L 600 88 Z"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 70 60 L 130 60"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 170 60 L 230 60"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 670 60 L 730 60"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 670 60 L 680 60 Q 700 60 700 80 L 700 140 Q 700 160 720 160 L 730 160"/>
 <circle cx="50" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="150" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#ffcdea"/>
 <circle cx="250" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#ff69c0"/>
 <circle cx="650" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="750" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="750" cy="160" r="20" stroke-width="4" stroke="#2f332b" fill="#ffcdea"/>
 <text class="svg20220701-14-t1" x="150" y="20" fill="#2f332b" text-anchor="middle">feature</text>
 <text class="svg20220701-14-t1" x="250" y="20" fill="#2f332b" text-anchor="middle">workspace</text>
 <text class="svg20220701-14-t1" x="750" y="20" fill="#2f332b" text-anchor="middle">feature</text>
</svg>
</div>

---

# Amend

<pre>repo (feature *)$ git log --oneline feature
3c68932 (HEAD -> feature) Some change
f887d61 Base
repo (feature *)$ git add .
repo (feature +)$ git commit --amend --no-edit
[feature ad3d11e] Some change
 Date: Tue Jun 21 20:20:05 2022 +0100
 1 file changed, 1 insertion(+), 1 deletion(-)
repo (feature)$ git log --oneline feature
ad3d11e (HEAD -> feature) Some change
f887d61 Base
repo (feature)$ 
</pre>

---

# Force push

<div align="center">
<svg xmlns="http://www.w3.org/2000/svg" id="svg20220701-15-1" width="100%" viewBox="0 0 1200 200">
 <style>
 #svg20220701-15-1 {
 border: 1px solid #e8e8e8;
 background-color: #f5f5f5;
 }
 .svg20220701-15-t1 {
 font-family: sans-serif;
 font-size: 16px;
 font-weight: bold;
 dominant-baseline: middle;
 }
 </style>
 <path stroke="none" fill="#ffffff" d="M 0 32 L 172 32 L 200 60 L 172 88 L 0 88 Z"/>
 <path stroke="none" fill="#ffffff" d="M 600 32 L 772 32 L 800 60 L 772 88 L 600 88 Z"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 70 60 L 130 60"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 70 60 L 80 60 Q 100 60 100 80 L 100 140 Q 100 160 120 160 L 130 160"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 670 60 L 730 60"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 670 60 L 680 60 Q 700 60 700 80 L 700 140 Q 700 160 720 160 L 730 160"/>
 <circle cx="50" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="150" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="150" cy="160" r="20" stroke-width="4" stroke="#2f332b" fill="#ffcdea"/>
 <circle cx="650" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="750" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="750" cy="160" r="20" stroke-width="4" stroke="#2f332b" fill="#ffcdea"/>
 <text class="svg20220701-15-t1" x="150" y="120" fill="#2f332b" text-anchor="middle">origin</text>
 <text class="svg20220701-15-t1" x="150" y="20" fill="#2f332b" text-anchor="middle">feature</text>
 <text class="svg20220701-15-t1" x="750" y="20" fill="#2f332b" text-anchor="middle">origin,feature</text>
</svg>
</div>

---

# Force push

<pre>repo (feature<>)$ git log --oneline --graph feature origin/feature
* ba4d6e8 (HEAD -> feature) Better change
| * 5b38ed3 (origin/feature) Some change
|/ 
* b766375 Base
repo (feature<>)$ git push
 ! [rejected] feature -> feature (non-fast-forward)
...
repo (feature<>)$ git push --force
...
 + 5b38ed3...ba4d6e8 feature -> feature (forced update)
repo (feature=)$ git log --oneline --graph feature origin/feature
* ba4d6e8 (HEAD -> feature, origin/feature) Better change
* b766375 Base
repo (feature=)$ 
</pre>

---

# Add -p

<div align="center">
<svg xmlns="http://www.w3.org/2000/svg" id="svg20220701-16-1" width="100%" viewBox="0 0 1200 200">
 <style>
 #svg20220701-16-1 {
 border: 1px solid #e8e8e8;
 background-color: #f5f5f5;
 }
 .svg20220701-16-t1 {
 font-family: sans-serif;
 font-size: 16px;
 font-weight: bold;
 dominant-baseline: middle;
 }
 </style>
 <path stroke="none" fill="#ffffff" d="M 0 32 L 72 32 L 100 60 L 72 88 L 0 88 Z"/>
 <path stroke="none" fill="#ffffff" d="M 600 32 L 772 32 L 800 60 L 772 88 L 600 88 Z"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 70 60 L 80 60 Q 100 60 100 80 L 100 140 Q 100 160 120 160 L 130 160"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 670 60 L 730 60"/>
 <path stroke-width="4" fill="none" stroke="#2f332b" d="M 770 60 L 780 60 Q 800 60 800 80 L 800 140 Q 800 160 820 160 L 830 160"/>
 <circle cx="50" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <path stroke="#2f332b" stroke-width="1" fill="#ff36ab" d="M 150 140 A 20 20 0 0 0 150 180 Z"/>
 <path stroke="#2f332b" stroke-width="1" fill="#ffcdea" d="M 150 140 A 20 20 0 0 1 150 180 Z"/>
 <circle cx="150" cy="160" r="20" stroke-width="4" stroke="#2f332b" fill="none"/>
 <circle cx="650" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="750" cy="60" r="20" stroke-width="4" stroke="#2f332b" fill="#ff36ab"/>
 <circle cx="850" cy="160" r="20" stroke-width="4" stroke="#2f332b" fill="#ffcdea"/>
 <text class="svg20220701-16-t1" x="50" y="20" fill="#2f332b" text-anchor="middle">feature</text>
 <text class="svg20220701-16-t1" x="150" y="120" fill="#2f332b" text-anchor="start">workspace</text>
 <text class="svg20220701-16-t1" x="750" y="20" fill="#2f332b" text-anchor="middle">feature</text>
 <text class="svg20220701-16-t1" x="850" y="120" fill="#2f332b" text-anchor="start">workspace</text>
</svg>
</div>

---

# Add -p

<pre>repo (feature *)$ git diff a.txt
...
-qui
-dolorem
+lorem
 ipsum,
...
 numquam
-[do]
+do
 eius
...
</pre>

---

# Add -p

<pre>repo (feature *)$ git add -p a.txt
...
-qui
-dolorem
+lorem
 ipsum,
...
(1/2) Stage this hunk [y,n,q,a,d,j,J,g,/,e,?]? y
...
 numquam
-[do]
+do
 eius
...
(2/2) Stage this hunk [y,n,q,a,d,K,g,/,e,?]? n

repo (feature *+)$ 
</pre>

---

# Add -p

<pre>repo (feature *+)$ git commit -m 'Some commit'
[feature 4660ca5] Some commit
 1 file changed, 1 insertion(+), 2 deletions(-)
repo (feature *)$ git diff a.txt
...
 numquam
-[do]
+do
 eius
 modi
...
repo (feature *)$ 
</pre>

---

# Delete unused branches

<pre>repo (develop=)$ git branch
* develop
 feature
repo (develop=)$ git branch -d feature 
Deleted branch feature (was 4660ca5).
repo (develop=)$ git push origin --delete feature
 - [deleted] feature
repo (develop=)$ git pull --prune
 - [deleted] (none) -> origin/another_feature
Already up-to-date.
repo (develop=)$ 
</pre>

---

# How to mess up

---

# How to mess up

<pre>repo (feature)$ git log --graph --oneline feature develop
* 3438fc3 (HEAD -> feature) Some change
* 23ee7fe (origin/develop, develop) Base
repo (feature)$ 
</pre>

- "Mircea showed me how to fast forward merge"

---

# How to mess up

<pre>repo (feature)$ git checkout develop
Switched to branch 'develop'
Your branch is up-to-date with 'origin/develop'.
repo (develop=)$ git merge --ff-only feature
Updating 23ee7fe..3438fc3
Fast-forward
 a.txt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
repo (develop>)$ git log --graph --oneline feature develop
* 3438fc3 (HEAD -> develop, feature) Some change
* 23ee7fe (origin/develop) Base
repo (develop>)$ git push
</pre>

---

# How to mess up

<pre>repo (develop>)$ git push
 ! [rejected] develop -> develop (fetch first)
error: failed to push some refs to '/home/mircea/Desktop/temp/repo.git'
hint: Updates were rejected because the remote contains work that you do
hint: not have locally. This is usually caused by another repository pushing
hint: to the same ref. You may want to first integrate the remote changes
hint: (e.g., 'git pull ...') before pushing again.
hint: See the 'Note about fast-forwards' in 'git push --help' for details.
repo (develop>)$ 
</pre>

- "git told me to"

---

# How to mess up

<pre>repo (develop>)$ git pull
...
 23ee7fe..615b3b4 develop -> origin/develop
Merge made by the 'recursive' strategy.
 b.txt | 0
 1 file changed, 0 insertions(+), 0 deletions(-)
 create mode 100644 b.txt
repo (develop>)$ git push
...
 615b3b4..0e030a7 develop -> develop
repo (develop=)$ 
</pre>

---

# How to mess up

<pre>repo (develop=)$ git log --graph --oneline feature develop
* 0e030a7 (HEAD -> develop, origin/develop) Merge branch 'develop'
|\ 
| * 615b3b4 Other change
* | 3438fc3 (feature) Some change
|/ 
* 23ee7fe Base
repo (develop=)$ 
</pre>

- wrong first parent
- this can happen when merging from develop into feature before fast forwarding develop to feature
- this can happen when pulling feature branch where two users collaborate
- you can do worse than this

- in this particular case resetting the local `develop` to the remote one after
  `pull`, but before `push` allows you to start again

<pre>repo (develop>)$ git reset --hard origin/develop
HEAD is now at 615b3b4 Other change
repo (develop=)$ 
</pre>

---
class: large-points
# Tip #11

- the point of the tactics is to create a clean history that matches the
  branching strategy, by addressing mistakes/issues on private branches (in
  a real, imperfect world)
- examples real world scenarios:
  - last commit on a feature branch fails a test, it needs a fix
  - we mix multiple issues in the same feature branch, we could regroup changes
  - developing/testing or code review/pull requests for a feature takes longer,
    will the merge to develop be green?

---
class: large-points
# Last tip

- don't follow recipes blindly
- understand what you do
- this was not a complete tutorial, some additional steps left out
- the particular steps depend on the situation
- be a responsible grown up, don't blame me :)
- don't draw simplistic, but wrong and dogmatic conclusions e.g. "never squash,
  we did it once, it went wrong, squash is bad"
- circle of competence/different for different people

---

# Questions?