Description
Subject of the issue
Working with git worktree via ruby-git corrupts repository index: previously clean original branch has files deleted/modified and reverse changes unstaged, new worktree has the same problems.
Your environment
git version 2.38.1
git (1.18.0)
ruby 2.7.7p221 (2022-11-24 revision 168ec2b1e5) [x86_64-linux]
Steps to reproduce
For demonstration I've created new repository with two branches, second 1 commit ahead of first, and from that second branch I've added worktree with first branch in a new directory - after that both worktrees became dirty.
user@localhost [/tmp] $ D=`mktemp -d`; echo $D; cd $D
/tmp/tmp.pwtopGh59g
user@localhost [/tmp/tmp.pwtopGh59g] $ git init
Initialized empty Git repository in /tmp/tmp.pwtopGh59g/.git/
user@localhost [/tmp/tmp.pwtopGh59g] $ echo "1.0" > VERSION; git add VERSION ; git commit -m "init commit"
[master (root-commit) a85add1] init commit
1 file changed, 1 insertion(+)
create mode 100644 VERSION
user@localhost [/tmp/tmp.pwtopGh59g] $ git checkout -b new-version
Switched to a new branch 'new-version'
user@localhost [/tmp/tmp.pwtopGh59g] $ echo "2.0" > VERSION; git add VERSION; git commit -m "new version"
[new-version 87dbf0e] new version
1 file changed, 1 insertion(+), 1 deletion(-)
user@localhost [/tmp/tmp.pwtopGh59g] $ D=`mktemp -d`; echo $D
/tmp/tmp.HbaM98rzYd
user@localhost [/tmp/tmp.pwtopGh59g] $ irb
2.7.7 :001 > require 'git'
=> true
2.7.7 :002 > g = Git.open('.')
=>
#<Git::Base:0x000056325dcc6880
...
2.7.7 :003 > g.worktree('/tmp/tmp.HbaM98rzYd', 'master').add
=> "Preparing worktree (checking out 'master')\nHEAD is now at a85add1 init commit"
2.7.7 :004 > exit
user@localhost [/tmp/tmp.pwtopGh59g] $ git status
On branch new-version
Changes to be committed:
(use "git restore --staged <file>..." to unstage)
modified: VERSION
Changes not staged for commit:
(use "git add <file>..." to update what will be committed)
(use "git restore <file>..." to discard changes in working directory)
modified: VERSION
58F3
user@localhost [/tmp/tmp.pwtopGh59g] $ git diff
diff --git a/VERSION b/VERSION
index d3827e7..cd5ac03 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-1.0
+2.0
user@localhost [/tmp/tmp.pwtopGh59g] $ git diff HEAD
user@localhost [/tmp/tmp.pwtopGh59g] $ cd /tmp/tmp.HbaM98rzYd
user@localhost [/tmp/tmp.HbaM98rzYd] $ git status
On branch master
Changes to be committed:
(use "git restore --staged <file>..." to unstage)
deleted: VERSION
Untracked files:
(use "git add <file>..." to include in what will be committed)
VERSION
user@localhost [/tmp/tmp.HbaM98rzYd] $ git diff
user@localhost [/tmp/tmp.HbaM98rzYd] $ git diff HEAD
diff --git a/VERSION b/VERSION
deleted file mode 100644
index d3827e7..0000000
--- a/VERSION
+++ /dev/null
@@ -1 +0,0 @@
-1.0
Expected behaviour
Original and new worktrees are clean
Actual behaviour
Original and new worktrees are dirty, although files were not actually changed, only its status in index
Investigation
This case almost blew my brain out, I was debugging with strace to see which git commands ruby-git executes, and when I ran the same commands by hand - everything worked as expected, i.e. both worktrees were clean. But after thorough examination I found out that ruby-git adds three environment variables: GIT_DIR, GIT_WORK_TREE and GIT_INDEX_FILE. The first two were duplicated by command-line options --git-dir and --work-tree, but the last one was the root of the problem: it points to index file in the original worktree while new worktree should use its own index.
I'm unsure whether that environment variable is needed at all, because GIT_DIR should be enough. But for sure it should be treated separately when working with git worktree.