Ben's Git tips

This is a collection of mostly intermediate-level tips and tutorials I have found since starting to use git.

Multiple remote repositories

Perhaps you have a repo with a remote called "origin" but you want to fetch changes from a different repo. You need to add the second repo manually:

1. Add the second repo as a remote called "reponame"

   git remote add reponame git@git:wx2_origin  # or a repo directory, e.g. /path/to/repo
   

2. List the remotes it knows about: it should have the original repo and the one you added.

   git remote -v
   

3. Fetch the branch remote_branch from reponame and call it local_branch locally. (E.g. both local_branch and remote_branch might be called VERSION_80100.)

   git fetch reponame remote_branch:local_branch
   

   Now you can switch to local_branch or cherry pick from it.

4. You can then pull changes from the remote or push your changes using:

   git pull origin      # Pull from "origin"
   git push origin
   git pull reponame    # Pull from "reponame"
   git push reponame
   

Diff including changes you have staged

If you have staged changes using git add then they stop showing up in git diff. To see them use:

git diff --cached

Search for a commit with a message/patch containing a string

Search for commits whose messages match the regexp <foo>:

git log --grep=<foo>

Search for commits whose patch (changes added or removed) matches the regexp <bar>:

git log -G<bar>

Ignore whitespace changes

The -w option to git show, git diff and git blame ignores whitespace changes, which can considerably simplify the output.

Switch to most recent branch

git checkout - will switch to the previous branch you were on, so you can you it to switch between two branches. (This is just like cd - but for branches instead of directories.)

Referencing a commit by regexp

You can reference a git commit using :/<regexp>, a regexp search for the pattern <regexp> in the commit texts (not just the title) for the youngest matching commit which is reachable from any ref. Note that this might be in a different branch, and it will be the newest one if there are multiple matches. E.g. git show :/IS_NUMBER. (See git help revisions.)

Git bisect following one branch

To do git bisect on just the first parent, mark the other parents as bad: see https://stackoverflow.com/a/5652323/ for details.

Git bisect within one commit

If a commit is too complicated you can split it up and bisect individual chunks: see https://gist.github.com/wisq/0fa021df52a3bd2485ac for details.

(You might find that most of the partial commits don't compile. If so, try to separate out the header file changes, or whatever, as necessary first.)

Patching from another repo

If you want to take changes from another repo but don't want to add it as a remote you can add changes using patches.

NB The following require the git apply to be called from the top-level directory of the destination repo otherwise it will fail silently.

To create a patch:

cd sourcerepo && git format-patch <commit1>..<commit2> > patchfile

To apply a patch:

cd destrepo && git apply patchfile

Do both in one command:

(cd sourcerepo && git format-patch --stdout <commit1>..<commit2>) | (cd destrepo && git apply -)

For uncommitted changes;

(cd sourcerepo && git diff) | (cd destrepo && git apply -)

I want to have several checked out trees but one git repo

Use git worktree.

Pushing excluding the last commit(s)

Perhaps you have commits that you want to push but the most recent one is experimental and you want to hold back on it.

git push origin HEAD^:<branch_name>

In general to push everything up to and including some earlier commit:

git push origin <commit>:<branch_name>

The merge results are too confusing

When doing a merge these special filenames become available to git show and git diff:

• The common ancestor is :1:<filename>
• The HEAD version is :2:<filename>
• The MERGE_HEAD version is :3:<filename>

I'm resolving a merge conflict but munged the file

If you edit a file with conflict markers (>>>>>>>, etc.) to resolve a merge conflict but mess it up you can ask git to re-create it using:

git checkout -m <filename>

Git reset and reflog

To deal with e.g. an undesired merge and push:

• Before doing any of these commands use git status to check you haven't got any uncommitted changes. If you have, or in any case, stash them and/or take a backup.
• You can use git reset --hard <ref> to move the current branch (and HEAD) to point to a different commit <ref>, in this example (eventually!) the one before the merge.
• You can use git log to see commit refs for commits on the current branch that you might want to move back to.
• Or you can use git reflog which shows all the previous commits HEAD has pointed to, which might not be on the current branch (e.g. if you've just done a regrettable rebase or reset).
• If you have rewritten history before the origin's HEAD it won't let you push so you need to use git push -f <origin> <branch>.

Git has forgotten renames after "git stash pop"

See http://stackoverflow.com/questions/8495103/git-stash-and-pop-shows-file-no-longer-marked-as-moved

git rm --cached file1

I've popped and lost (or dropped) a git stash and want it back

Look at these commits, which are the dangling commits (not yet garbage collected) for ones with a title like WIP on <somebranch>: <commithash> <commit message>.

git fsck --no-reflog | awk '/dangling commit/ {print $3}'

This is more pleasant using gitk:

gitk --all $( git fsck --no-reflog | awk '/dangling commit/ {print $3}' )

Then you can use git stash apply <hash> to apply it (or perhaps git stash store <hash> to save it).

I want my repo to be readable by people in my group or everybody

Set git config option core.sharedRepository to group or all. For gitolite 3 use $UMASK. See https://stackoverflow.com/questions/7086325/setting-umask-in-git-gitolite

Git thinks a file has changed but you don't agree

Perhaps you're trying to switch branch and git says you can't because a file has changed, but git diff doesn't show any differences and git stash says nothing has changed.

This can happen if the file has a filter on it and its timestamp has changed, and it is different from the version in the repo although the "clean" filter version isn't different. If you're sure then fix using:

git checkout -f <file>

I want to display git context in my prompt

Download git-prompt.sh, if you don't already have it as part of your git distribution, and follow the instructions in the comment at the start.

General references and tutorials

• Pro Git book website, GitHub page and PDF
• Git for Ages 4 And Up
• Explanation of git remote branches and rejected push error

Problem-fixing tutorials

Every change that git is told about, including "git add" and "git stash", is saved in git. You should be able to recover from most mistakes using "git reflog" and "git show" together with "git reset", "git checkout" or "git cherry-pick".

• Reflog, your safety net
• Recovering lost commits with git reflog and reset
• Use "git reflog" and "git cherry-pick" to restore lost commits
• On undoing, fixing, or removing commits in git in the style of "choose your own adventure"
• "Flight rules" for Git

Tutorials on Git internals

• Disecting Git's Guts
• Git from the Inside Out essay and talk
• Advanced Git: Graphs, Hashes and Compression, Oh My!
• Git from the bottom up