Applying patch: git apply, worktrees and invalid gitdir

[e1senh0rn]

I'm using recently released worktrees git feature, and having issues with applying patches.
Also I use Vagrant, and it renders gitdir path within worktree invalid.

Here is an example.

mkdir /tmp/git_apply_issue
cd /tmp/git_apply_issue
# Simulate worktree with invalid path
echo 'gitdir: /nonexistent' > .git
echo "source 'https://rubygems.org'\n\ngem 'nokogiri'" > Gemfile
bundle install --path ./.bundle

# Extracting libxml2-2.9.2.tar.gz into tmp/x86_64-apple-darwin15.2.0/ports/libxml2/2.9.2... OK
# Running git apply with /tmp/git_apply_issue/.bundle/ruby/2.3.0/gems/nokogiri-1.6.7.2/patches/libxml2/0001-Revert-Missing-initialization-for-the-catalog-module.patch... ERROR, review '/tmp/git_apply_issue/.bundle/ruby/2.3.0/gems/nokogiri-1.6.7.2/ext/nokogiri/tmp/x86_64-apple-darwin15.2.0/ports/libxml2/2.9.2/patch.log' to see what happened. Last lines are:
# ========================================================================
# fatal: Not a git repository: /nonexistent
# ========================================================================
...

I believe it is caused by behavior of git apply itself. Apparently --work-tree=. does not prevent git from traversing up and looking for git repo files.

git apply command is being executed within /tmp/git_apply_issue/.bundle/ruby/2.3.0/gems/nokogiri-1.6.7.2/ext/nokogiri.

Is there a way to avoid this error?

[flavorjones]

@e1senh0rn Thanks for asking this question.

I don't totally understand what you're demonstrating above ... that git apply blows up if you have gitdir set to a nonexistent directory? This seems a little contrived. Can you help me understand a real use case?

[e1senh0rn]

You are correct, git apply just blows up. Actually, patch works just fine.

Here is what I'm doing.
I have rails project (cloned from git repo) in /Users/eisenhorn/work/project.
I create another branch to play with vagrant. Switching branches during daily work leads me to bunch of issues like removed .vagrant folder, overwritten project configs, etc.
To avoid it I create worktree with vagrant branch in /Users/eisenhorn/work/project-vagrant (via git worktree add ../project-vagrant vagrant).
Everything looks very smooth, I just change dir and keep working (start vm, provision, run app, etc).

In Vagrantfile I'm mapping /Users/eisenhorn/work/project-vagrant into VM as /home/vagrant/app. That is why .git file has completely broken gitdir specification within VM.

Finally, in VM I execute bundle install --path /home/vagrant/app/.bundle, and nokogiri installation fails because of bundled libxml/libxslt and mini_portile applying patches via git apply. Git traverses up, encounters invalid gitdir, and fails.