Git

Mastering GitHub course

git pull
- git fetch
- git merge
git pull --rebase
- git fetch
- git rebase
keeping in sync (on every accepted pull req in upstream repo)
- add remote for upstream: git remote add upstream <path_to_repo>
- pull changes: git pull upstream master
  - fetch changes: git fetch upstream
  - merge them into master: git merge upstream/master master
- push them to your remote: git push origin master

Atlassian tutorials

git add helps to create atomic commits
- modify a bunch of files
- stage related changes only
- commit
- repeat...
~: relative reference operator
- HEAD~3: great-grandparent of current commit
- 3157e~1: commit before 3157e
..: range operator
- git log <since>..<until>: show commit log b/w 2 commits
- git log --oneline master..some-feature: show all commits which are in some-feature branch but not in master
misc

# create empty repo w/o working dir (for central repos, not for development)
# dir usually ends in .git
git init --bare <dir>

# stage chunks of a file interactively
git add -p

# add and commit tracked files only
git commit -am "msg"

# show which files were altered
git log --stat

# show patch/diff
git log -p

# filter log
git log --author="<pattern>"
git log --grep="<pattern>"

# specific file only
git log myfile.py

Undoing Changes

undo
- unstage: git reset HEAD <file>
- discard changes in work dir: git checkout -- <file>
git checkout
- commits: git checkout <commit>
  - makes entire work dir (all files) match commit
  - enters "detached HEAD" state! (HEAD points to a commit now, not a branch)
  - read-only operation, doesn't affect current state of project
  - effectively, changes the snapshot you are working on
  - go back to current snapshot: git checkout master
- files: git checkout <commit> <file>
  - shows old version of a file
  - adds to staging area
  - not ready-only, affects current state of project
  - can revert to old file version by committing
  - go back to latest version: git checkout HEAD <file>
- branches: git checkout master
git revert <commit>
- safe: it doesn't change project history
- designed to fix public commits, it does not rewrite history
- to "remove" an entire single (and public) commit anywhere in history
- it does not revert back to a previous state of a project
- to revert last commit: git revert HEAD
git reset
- dangerous and permanent, can lose work
- designed to fix local commits and unstaged changes
  - unstaging a file
  - removing a local commit
- use only to undo local changes
- most often used to undo changes in staging and work dir, not committed snapshots
- can only work backwards from the current commit
- git resett <file>: remove file from staging (but don't overwrite changes!)
- git reset: reset the whole staging area to match latest commit (but don't overwrite work dir changes!) so you can rebuild staged snapshot
- git reset --hard: unstage all and obliterate all uncommitted changes
- git reset <commit>: move HEAD to , reset staging, leave work dir alone so you can re-commit with more atomic snapshots
- git reset --hard <commit>: move HEAD to , reset both staging area and working dir (obliterates all changes after )
- git reset --hard HEAD~2: remove 2 last commits
- never reset a public commit: don't git reset <commit> after git push
git clean
- can be dangerous, not undoable
- remove untracked files from working dir
- used with git reset --hard to return work dir to state of last commit
- git clean -n: dry run (don't remove)
- git clean -f: force is required for removing by default; doesn't work for .gitignore files/dirs
- git clean -f <path>: remove only files in
- git clean -df: remove both untracked files and dirs
- git clean -xf: remove untracked files and ignored files

Rewriting History

git commit --amend
- combine staged changes with last (previous) commit to create a brand new commit
- never amend public commits!
- don't change last commit msg: git commit --amend --no-edit
git rebase
- move a branch to a new base commit in order to maintain a linear project history
- common way to integrate upstream changes into a local repo
- git rebase <base>: where can be
  - ID
  - branch name
  - tag
  - relative ref to HEAD
- options when master branch has progressed since branch started
  - merge directly: 3-way merge + merge commit
  - rebasing and then merging: fast-forward merge (resulting in linear history)
- never rebase public commits!
- git rebase -i <base>: interactive rebasing (alter individual commits)
  - gives complete control over project history
  - use to polish a feature branch before merging in master
- git rebase --continue: continue rebase after resolving conflicts
- git rebase --abort: abort rebase; will rollback to state before rebase cmd
git reflog
- show reflog (history of HEAD changes, branch checkouts, merges, etc.)
- show reflog with relative dates: git reflog --relative-date

Syncing

git remote
- git remote -v: see all remotes
- git remote add <name> <url>: add remote origin
- git remote rm <name>: remove remote origin
- git remote rename <old-name> <new-name>: rename remote origin
git fetch
- git fetch <remote> <branch>: fetch a remote branch to inspect (can checkout locally)
- to explore origin changes before merging
  - git fetch origin: fetch remote's master branch w/o merging
  - git log --oneline master..origin/master: see new commits
  - git checkout master: go to master branch
  - git log origin/master: see log
  - git merge origin/master: merge
git pull
- git pull <remote>: fetch and merge
  - git fetch <remote>
  - git merge origin/<current-branch>
- git pull --rebase <remote>: rebase instead of merge
  - to ensure a linear history (prevents unnecessary merge commits)
- git config --global branch.autosetuprebase always: turn on rebasing during a pull
- move local changes onto pulled ones
  - git checkout master
  - git pull --rebase origin
- if a git pull upstream develop does a merge commit
  - git reset --hard HEAD~1: remove last merged commit (only if you haven't pushed)
  - git pull --rebase updtream develop: fetch and rebase upstream (canonical repo) instead of merge
  - git pull --rebase: fetch and rebase origin (forked repo)
git push
- git push <remote> <branch>: push branch
  - creates a local branch in dest repo
  - prevents push if merge in dest repo is non-fast-forward
  - if remote history has diverged, pull remote and then push again
- git push <remote> --force: force push
  - dangerous and destructive
  - merge in dest repo even if merge is non-fast-forward
  - it will delete upstream changes and make remote repo the same as local one
  - use case
    - just committed something which nobody else has pulled
    - then did git commit --amend or interactive rebase
    - and now git push --force to overwrite remote
- git push <remote> --all: push all local branches to remote
- git push <remote> --tags: push tags too
- git push -u origin my-feature
  - push a local branch as a remote tracking branch
  - specify -u origin my-feature first time only
- only push to bare repos, never push to a normal one
- example
  - git checkout master: be in master branch
  - git fetch origin master: fetch w/o merging
  - git rebase -i origin/master: clean up/squash commits using interactive rebase of local commits on top of pulled ones (instead of merging)
  - git push origin master

Using Branches

git branch
- git branch: list all branches
- git branch <branch>: create new branch w/o checking it out
- git branch -d <branch>: delete branch as long as no unmerged changes
- git branch -D <branch>: force delete branch with unmerged changes
- git branch -m <branch>: rename branch
- a branch is a ref/ptr to a commit
- the tip of a series of commits, not a container for commits
git checkout
- git checkout <existing-branch>: check out already created branch
- git checkout -b <new-branch>: check out new branch
- git checkout -b <new-branch> <existing-branch>: base new branch on existing instead of current one
- development should always take place on a branch, never on a detached HEAD as you can't merge those commits back into trunk
git merge
- merg into the current branch leaving the target branch unaffected
- git merge <branch>: merge specified branch into current branch
- git merge --no-ff <branch>: always generatea a merge commit (even on fast-forward merges)
- a fast-forward merge
  - moves the current branch tip up to the target branch tip
  - use for small features and bug fixes
- a 3-way merge
  - uses 3 commits to generate merge commit (2 branch tips + common ancestor)
  - resolving merging conflicts using edit/stage/commit workflow
  - use for longer-running features
  - to prevent 3-way merging (and superfluous merge commits)
    - rebase
    - do a fast-forward merge
- example
  - git checkout -b new-feature master: create and checkout new branch
  - edit/stage/commit
  - git checkout master: got back to master
  - git merge new-feature: merge new feature branch into master
  - git branch -d new-feature: delete feature branch

Workflows

Gitflow Workflow
- create empty develop branch
  - git branch develop
  - git push -u origin develop
- clone central repo and create a tracking branch
  - git clone <repo>
  - git checkout -b develop origin/develop
- base feature branches on develop, not master!
  - git checkout -b some-feature develop
- pull request or merge in develop branch only!
  - git pull origin develop: make sure up to date before merging
  - git checkout develop
  - git merge some-feature: in develop, not master!
  - `git push
  - git branch -d some-feature
- prepare a release
  - git checkout -b release-0.1 develop
- finish the release by merging into master AND develop
  - git checkout master
  - git merge release-0.1
  - git push
  - git checkout develop
  - git merge release-0.1
  - git push
  - git branch -d release-0.1
  - git tag -a 0.1 -m "initial public release" master: tag release
  - git push --tags
- bug fixes get merged directly into master AND develop
  - git checkout -b issue-#001 master: base off of master
  - edit/stage/commit
  - git checkout master
  - git merge issue-#001
  - git push
  - git checkout develop: merge in develop too!
  - git merge issue-#001
  - git push
  - git branch -d issue-#001

Commands

# Per @jferris: `ff = only` means Git will never implicitly do a merge commit, including while
# doing git pull. If I'm unexpectedly out of sync when I git pull, I get this
# message:
# fatal: Not possible to fast-forward, aborting.
# At that point, I know that I've forgotten to do something in my normal
# workflow, and I retrace my steps.

# to merge a file (outside any branch because its branch was deleted)
# to the master branch
git checkout master
git merge <hash of commit>

# amend an older commit
git rebase --interactive bbc643cd^
# In the default editor, modify 'pick' to 'edit'
# in the line whose commit you want
# to modify. Make your changes and then stage them with
git add <filepattern>
git commit --amend
git rebase --continue

# rename remote URL
git remote set-url origin https://github.com/vgslavov/MS-thesis.git

# replace
# local changes (with last content in HEAD)
git checkout -- file.txt
# - drop all local changes and commits
# - fetch latest history from server
# - point local master branch at it
git fetch origin
git reset --hard origin/master

# remove a file from the staging area
git reset <filename>

# unstage
git reset HEAD <filename>

##############################
# DON'T DO THESE AFTER PUSH! #

# reset into staging and move to commit before HEAD
# (undo last commit, put changes into staging)
git reset --soft HEAD^

# amend commit message only
# (change the last commit)
git commit --amend -m "New commit message"

# undo last commit and all changes
git reset --hard HEAD^

# undo last 2 commits and all changes
git reset --hard HEAD^^

##############################

# don't forget the quotes (to prevent the shell from expanding *)
git add "*.txt"
# interactive adding
git add -i

# add all (even in parent dirs)
git add --all

# create branch
git branch cat

# see branches
git branch

# switch to a branch
git checkout cat

# merge to mmaster
git checkout master
git merge cat

# delete branch when done
git branch -d cat

# create a new repository on the command line
touch README.md
git init
git add README.md
git commit -m "first commit"
git remote add origin https://github.com/vgslavov/try_git.git
# show remote repositories
git remote -v
# push local branch 'master' to remote repository 'origin'
git push -u origin master

# push an existing repository from the command line
git remote add origin https://github.com/vgslavov/try_git.git
git push -u origin master

# -u: remember parameters (name of origin repository)
git push -u origin master

# don't commit, stash instead (if not sure)
git stash
# re-apply after pull
git stash apply

# what's different from last commit (after pull)
git diff HEAD

# keep related changes in separate commits:
# use 'get diff' before starting to 'add'

# see only staged changes
git diff --staged

# unstage files
git reset file.txt

# get rid of all changes since last commit
# ('--' tells git no more options after)
git checkout -- file.txt

# auto remove deleted files (which were not deleted using 'git rm')
git commit -am "Delete stuff"

# can't delete (-d) a branch which has not been merged, so use -D (-d -f)
git branch -D bad_feature

# log
# see log+diff
git log --oneline --patch
git log --oneline --stat
git log --since=2012-01-01 --until=2012-12-21

# diff
# b/w last commit and current state (both staged and unstaged)
git diff HEAD
# parent of latest commit
git diff HEAD^
# grandparent
git diff HEAD^^
# specific file
git show HEAD^^:lib/tasks/sample_data.rake
# five commits ago
git diff HEAD~5
# second most recent vs. most recent
git diff HEAD^..HEAD
# b/w branches
git diff master mybranch

# who did what when
git blame index.html --date short

# untracking files (don't delete from local file system)
git rm --cached development.log

git log c5271 myfile
git checkout c5271 myfile

git branch -b int2POLY
git branch
...
git add .
git commit
git checkout master
git merge int2POLY
git push

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Git

Mastering GitHub course

Atlassian tutorials

Undoing Changes

Rewriting History

Syncing

Using Branches

Workflows

Commands

FilesExpand file tree

git.md

Latest commit

History

git.md

File metadata and controls

Git

Mastering GitHub course

Atlassian tutorials

Undoing Changes

Rewriting History

Syncing

Using Branches

Workflows

Commands