List and delete git branches without cloning

Question

for k in $(git branch -r --merged origin/master | cut -d" " -f 3); do
    echo $k
done

I have a list of git projects that i want to clean up old branches in, what i want to do is list and delete all the branches that are merged to master.

Is there a way to do the above without cloning each repo locally?

Answer 1

You need git ls-remote:

NAME

git-ls-remote - List references in a remote repository

SYNOPSIS

git ls-remote [--heads] [--tags] [--refs] [--upload-pack=<exec>]
              [-q | --quiet] [--exit-code] [--get-url]
              [--symref] [<repository> [<refs>...]]

DESCRIPTION

Displays references available in a remote repository along with the associated commit IDs.

So it works like:

% git ls-remote origin
af51dfb080728117d898e1d0a10e3fe01ed67063        HEAD
6a60cc68a2953f1a62b0dca641eb29509b5b6e8c        refs/heads/expdate-fix
af51dfb080728117d898e1d0a10e3fe01ed67063        refs/heads/master
4c42e43b4ccfd37074d115f6e9a694ddb8b70d55        refs/heads/redux
fd18a67bbc5cbf8aa6cda136afa4e5c20ed2d522        refs/heads/rest
7ad17cdf8b0dcd1a29a1795a363279fb3c76ac66        refs/tags/test.key
be0b2d6881902600fb3d6686c10d0a47f1e6751a        refs/tags/test.pub

To get only branches (heads), you need to narrow the refspec down:

% git ls-remote origin 'refs/heads/*'
6a60cc68a2953f1a62b0dca641eb29509b5b6e8c        refs/heads/expdate-fix
af51dfb080728117d898e1d0a10e3fe01ed67063        refs/heads/master
4c42e43b4ccfd37074d115f6e9a694ddb8b70d55        refs/heads/redux
fd18a67bbc5cbf8aa6cda136afa4e5c20ed2d522        refs/heads/rest

Now you could script around this output like

git ls-remote origin 'refs/heads/*' | while read sha ref; do
  # test if $sha is merged
done

To delete a branch, you need to "push nothing" to it, like in

git push origin :refs/heads/feature-x

(notice an empty string to the left of ":" which defined what to push to what is on the right side).

So we get something like

#!/bin/sh
set -e -u
git ls-remote origin 'refs/heads/*' | while read sha ref; do
  # test if $sha is merged
  E=`git cat-file -t "$sha" 2>&1`
  test $? -ne 0 -a "${E#*git cat-file: *}" = "could not get object info" && continue
  git branch --merged "$sha" && printf ':%s\0' "$ref"
done | xargs -0 git push origin

Note that we're using printf shell builtin to delimit the names of the refs we output with the ASCII NUL character and then pass -0 to xargs to expect NUL-terminated input. This way we work around funky ref names (containing spaces etc).

Some explanations:

• If git cat-file -t <object_sha1_name> fails to locate the object with the indicated SHA1 name in the local repository, it exits with a non-zero exit code and prints

  fatal: git cat-file: could not get object info

  to its stderr.

• So to test whether the history a remote ref points at exists in the local repository we run git cat-file -t on the SHA1 name of the object it points at, grab the combined output of that command and then test whether it exited with a non-zero exit code ($? -ne 0) and whether its error message indicates a missing object (the ${VAR#PATTERN} removes the prefix matching PATTERN from the contents of the variable VAR and returns the resulting value).

• If the history a remote ref points at does not exist in the local repository, it cannot be merged to any of the local refs by definition, so if we detect such a ref, we skip its further testing with git branch --merged.