Git Tricks

git-tricks.md

Git Tips & Tricks

Oups Tricks

The "I forgot something in my last commit" Trick

# first: stage the changes you want incorporated in the previous commit
 
# use -C to reuse the previous commit message in the HEAD
$ git commit --amend -C HEAD
# or use -m to make a new message
$ git commit --amend -m 'add some stuff and the other stuff i forgot before'

The "Oh crap I didn't mean to commit yet" Trick

# undo last commit and bring changes back into staging (i.e. reset to the commit one before HEAD)
$ git reset --soft HEAD^

The "That commit sucked! Start over!" Trick

# undo last commit and destroy those awful changes you made (i.e. reset to the commit one before HEAD)
$ git reset --hard HEAD^

The "Oh no I should have been working in a branch" Trick

# takes staged changes and 'stashes' them for later, and reverts to HEAD. 
$ git stash
 
# creates new branch and switches to it, then takes the stashed changes and stages them in the new branch.   fancy!
$ git stash branch new-branch-name

The "OK, which commit broke the build!?" Trick

# Made lots of local commits and haven't run any tests...
$ [unittest runner of choice]
# Failures... now unclear where it was broken.

# git bisect to rescue. 
$ git bisect start # to initiate a bisect
$ git bisect bad   # to tell bisect that the current rev is the first spot you know was broken.
$ git bisect good <some tag or rev that you knew was working>
$ git bisect run [unittest runner of choice]
# Some runs.
# BLAMO -- git shows you the commit that broke
$ git bisect reset #to exit and put code back to state before git bisect start
# Fix code. Run tests. Commit working code. Make the world a better place.

The "I have merge conflicts, but I know that one version is the correct one" Trick, a.k.a. "Ours vs. Theirs"

# in master
$ git merge a_branch
CONFLICT (content): Merge conflict in conflict.txt
Automatic merge failed; fix conflicts and then commit.
$ git status -s
UU conflict.txt
 
# we know the version of the file from the branch is the version we want.
$ git checkout --theirs conflict.txt
$ git add conflict.txt
$ git commit
 
# Sometimes during a merge you want to take a file from one side wholesale.
# The following aliases expose the ours and theirs commands which let you
# pick a file(s) from the current branch or the merged branch respectively.
#
# N.b. the function is there as hack to get $@ doing
# what you would expect it to as a shell user.
# Add the below to your .gitconfig for easy ours/theirs aliases. 
#    ours   = "!f() { git checkout --ours $@ && git add $@; }; f"
#    theirs = "!f() { git checkout --theirs $@ && git add $@; }; f"

Repository administration

The "Workaround Self-signed Certificates" Trick

# Issue: When attempting to clone (or any other command that interacts with the remote server) git by default validates 
# the presented SSL certificate by the server.  Our server's certificate is not valid and therefore git exits out with an error.
# Resolution(Linux): For a one time fix, you can use the env command to create an environment variable of GIT_SSL_NO_VERIFY=TRUE. 
$ env GIT_SSL_NO_VERIFY=TRUE git <command> <arguments>

# If you don't want to do this all the time, you can change your git configuration:
$ git config --global http.sslVerify false

The "I can never remember that alias I set" Trick

[alias]
	aliases = !git config --get-regexp 'alias.*' | colrm 1 6 | sed 's/[ ]/ = /' | sort

Split a subdirectory into a new repository/project

$ git clone ssh://stash/proj/mcplugins.git 
$ cd mcplugins
$ git checkout origin/master -b mylib
$ git filter-branch --prune-empty --subdirectory-filter plugins/mylib mylib
$ git push ssh://stash/proj/mylib.git mylib:master

Local Branch Cleanup

# Delete local branches that have been merged into HEAD
$ git branch --merged | grep -v '\\*\\|master\\|develop' | xargs -n 1 git branch -d
# Delete local branches that have been merged into origin/master
$ git branch --merged origin/master | grep -v '\\*\\|master\\|develop' | xargs -n 1 git branch -d
# Show what local branches haven't been merged to HEAD
$ git branch --no-merged | grep -v '\\*\\|master\\|develop'