I have a bare git repository setup for user fred:
/home/fred/foo.git
I have set the group of every file in foo.git to bar:
$ chown -R fred:bar /home/fred/foo.git
(Note that fred is not a member of group bar)
And I have set the setgid bit on for every directory in foo.git:
$ find foo.git -type d -print0 | xargs -0 chmod g+s
However when fred commits to the git repository, the group is not preserved in some files.
Specifically in the objects directory I see:
foo.git/objects:
drwxrws--- 46 fred bar 4096 Apr 7 23:43 .
drwxrws--- 7 fred bar 4096 Apr 6 17:12 ..
drwxrws--- 2 fred bar 4096 Apr 6 17:11 07
drwxrws--- 2 fred bar 4096 Apr 6 17:11 10
drwxrwx--- 2 fred bar 4096 Apr 7 22:14 14 <--- HERE
drwxrws--- 2 fred bar 4096 Apr 6 17:11 17
^--- HERE
Notice that in objects/14 the setgid bit is not set. So consequently when a new object is added to that directory:
foo.git/objects/14:
drwxrwx--- 2 fred bar 4096 Apr 7 22:14 .
drwxrws--- 46 fred bar 4096 Apr 7 23:43 ..
-r--r----- 1 fred fred 2595 Apr 7 22:14 95482f8..9d6bfe21
So now the 95482.. file doesn't have group bar, it has group fred.
I suspect that when fred commited, git created a new directory on-demand called objects/14 to hold a new object, when it did this for some unknown reason the setgid bit on the new 14 directory was not set, even though its parent directory objects has the setgid bit set.
If I try to reproduce this manually:
$ su fred # as user fred
$ mkdir test1 # create test1 dir
$ sudo chgrp bar test1 # set group to bar
$ sudo chmod g+s test1 # set setgid bit
$ ls -l
drwxrwsr-x 2 fred bar 4096 Apr 8 21:33 test1
$ mkdir test1/test2 # create dir test1/test2
$ ls -l
drwxrwsr-x 2 fred bar 4096 Apr 8 21:35 test2
^--- HERE
Notice the setgid bit in the new test1/test2 is preserved, so when I...
$ touch test1/test2/test3
The new file is still group bar as expected:
$ ls -l test1/test2
-rw-rw-r-- 1 fred bar 0 Apr 8 21:36 test3
Why doesn't git seem to preserve the setgid bit when it creates new directories in the .git directory?
Is there some git setting I can make to fix this? Or can you explain what is causing this?
It turns out that when you specify the core.sharedrepository config, git does chmod()s on the files it creates. That way, the result is correct despite filesystem types and mount options, except in your one case where the repository owner isn't a member of the group it's shared with.
That bad result happens because git's chmod() appears to succeed -- you can see it in an strace -- but ignores anything the issuing user isn't authorized to ask for.
So to avoid that weirdity, the thing to do is
git config --unset core.sharedrepository
(or not specify --shared at all on the init) so git doesn't touch the filesystem's default permissions at all. Amusingly enough that makes everything work:
~/sandbox/75276/s$ find ../s.git -ls
12193569 4 drwxrws--- 4 jthill mail 4096 Apr 9 13:52 ../s.git
12193571 4 -rw-rw---- 1 jthill mail 73 Apr 8 20:40 ../s.git/description
12193572 4 -rw-rw---- 1 jthill mail 23 Apr 8 20:40 ../s.git/HEAD
12721086 4 drwxrws--- 2 jthill mail 4096 Apr 9 13:52 ../s.git/objects
12193570 4 drwxrws--- 2 jthill mail 4096 Apr 9 13:52 ../s.git/refs
12193578 4 -rw-rw---- 1 jthill mail 104 Apr 9 13:37 ../s.git/config
~/sandbox/75276/s$ cat ../s.git/config
[core]
repositoryformatversion = 0
filemode = true
bare = true
[receive]
denyNonFastforwards = true
~/sandbox/75276/s$ git push origin master
Counting objects: 3, done.
Writing objects: 100% (3/3), 198 bytes, done.
Total 3 (delta 0), reused 0 (delta 0)
To /home/jthill/sandbox/75276/s.git
* [new branch] master -> master
~/sandbox/75276/s$ find ../s.git -ls
12193569 4 drwxrws--- 4 jthill mail 4096 Apr 9 13:52 ../s.git
12193571 4 -rw-rw---- 1 jthill mail 73 Apr 8 20:40 ../s.git/description
12193572 4 -rw-rw---- 1 jthill mail 23 Apr 8 20:40 ../s.git/HEAD
12721086 4 drwxrws--- 5 jthill mail 4096 Apr 9 13:53 ../s.git/objects
16777964 4 drwxrwsr-x 2 jthill mail 4096 Apr 9 13:53 ../s.git/objects/58
16777965 4 -r--r--r-- 1 jthill mail 17 Apr 9 13:53 ../s.git/objects/58/7be6b4c3f93f93c489c0111bba5596147a26cb
16777962 4 drwxrwsr-x 2 jthill mail 4096 Apr 9 13:53 ../s.git/objects/ab
16777963 4 -r--r--r-- 1 jthill mail 46 Apr 9 13:53 ../s.git/objects/ab/69b4abf3bb84d4e268bd42d84e4a9a5e242bd3
16777960 4 drwxrwsr-x 2 jthill mail 4096 Apr 9 13:53 ../s.git/objects/81
16777961 4 -r--r--r-- 1 jthill mail 120 Apr 9 13:53 ../s.git/objects/81/210f2df9629e5df5f6dfa0923a2cf72369314d
12193570 4 drwxrws--- 3 jthill mail 4096 Apr 9 13:53 ../s.git/refs
12193573 4 drwxrwsr-x 2 jthill mail 4096 Apr 9 13:53 ../s.git/refs/heads
12193574 4 -rw-rw-r-- 1 jthill mail 41 Apr 9 13:53 ../s.git/refs/heads/master
12193578 4 -rw-rw---- 1 jthill mail 104 Apr 9 13:37 ../s.git/config
~/sandbox/75276/s$
来源：https://stackoverflow.com/questions/15889573/setgid-bit-not-preserved-by-git-on-new-directory-in-git-folder