# GIT

Git is just a big directed acyclic graph DAG

Dont use LINUX like DOS

# Power of git

git rev-list : list commits on reverse chronological order

Suppose you have to rebase some of your commits. When you change the commits, would the tests still pass?

Did I break any code when I rebased the source?

( set -e && git rev-list --reverse master~3..master \
  | while read rev; do echo git checkout $rev; \
  python runtests.py; done)

OH: ITs half assed, but it is the right half of the ass.

::: theorem Power Law Distribution implies that small values are extremely common, whereas large values are extremely rare.

Primitives
Means of Combination
Means of abstraction :::

I want to know the count of references of classes and modules in codebase?

grep-ruby() { find app lib -name '*.rb' | xargs grep $* }
grep-ruby() -h '[[:space:]]*\(class\|module\)\b' |
  sed 's/^[[:space:]]*//' |
  cut -d ' ' -f 2
  while read class; do
    echo "`grep-ruby -l "\b$class\b" | wc -l` $class"

# Submodules

Git repository with in another git repository
Git commit history comes along with submodule repository

git submodule init
git submodule summary
git submodule status

$ git submodule add --name subOne -- git@github.com:avimehenwal/javascript.git docs/docs/posts
Cloning into '/home/avi/EXP/multiple-docs/docs/docs/posts'...
X11 forwarding request failed on channel 0
remote: Enumerating objects: 652, done.
remote: Counting objects: 100% (652/652), done.
remote: Compressing objects: 100% (365/365), done.
remote: Total 652 (delta 273), reused 617 (delta 241), pack-reused 0
Receiving objects: 100% (652/652), 6.33 MiB | 6.85 MiB/s, done.
Resolving deltas: 100% (273/273), done.

Dry run git commands before actually running them
- git rm --dry-run -r ~/aviscripts/

# Restore deleted files

git rm --dry-run --cached README.md

git restore --staged README.md && git restore README.md

# How to edit any commit message? or as a matter of fact rewrite entire git history

strategy is checkout to commit -> amend message -> then rebase back to HEAD

# abort on conflicts
git rebase ... || git rebase --abort

git rebase --interactive <commit hash you want to change>^
# then reword commit message

# First commit
git rebase --interactive --root

# Rebase last N commits
git rebase --interactive @~9

# checkout the root commit
git checkout <sha1-of-root>

# amend the commit
git commit --amend

# rebase all the other commits in master onto the amended root
git rebase --onto HEAD HEAD master

# Merging 2 repos into 1

subtree-merge or submodules

didn’t need the ability to extract changes and ship them back anywhere because my old repositories would be retired
fatal: refusing to merge unrelated histories
- git pull --allow-unrelated-histories

# In new git repo
git remote add one <url>
git pull --allow-unrelated-histories one master
find ! -path "./.git*" -exec mv -v --target-directory=one_repo {} +
mv -v .gitignore one_repo/

# Merge Strategies

using ours and theirs with -X | --strategy-option switch

merge-strategy Autoresolve merge conflicts

git merge --strategy-option theirs develop
git merge -X theirs develop

How do I merge A into B, without losing history on any side?

git subtree add --prefix=rails git://github.com/rails/rails.git master

This will appear as a single commit where all files of Rails master branch are added into "rails" directory. However the commit's title contains a reference to the old history tree:

# Git merge

Used when you have ammended/rebases commits on one branch which were already there in master. Performing merge normally will raise merge conflicts. To automatically force rewrite changes (rebased or ammended) from develop to master use this command below

git merge --progress --verbose --summary -X theirs develop

How to remove a commit from history?: Use rebase and delete the commit you do not want to pick
What is revert?: Reverting the changes made in a previous commit as a new commit

rebase

Very dangerous commands

How to undo a gitrebase?

Manually

Reference logs

git reflog
git reset --hard HEAD@{5}

How to check diff before raising PR?

git difftool --tool=meld --dir-diff master...

or use gitlens comparision with vscode

# 🌸 Cherrypicking

Useful when working on opensourced projects, you might want to keep personal changes in develop branch, but only cherry-pick certain commits to master branch for raising PR with upstream.

git cherry-pick <commitId> -n

# Reset

To rewind local changes
Time travelling
3 trees in git *

# Resources

← Text Editor Github Actions →