linux - setgid bit not preserved by git on new directory in `.git` folder? -

i have bare git repository setup user fred:

/home/fred/foo.git 

i have set group of every file in foo.git bar:

$ chown -r fred:bar /home/fred/foo.git 

(note fred not member of group bar)

and have set setgid bit on every directory in foo.git:

$ find foo.git -type d -print0 | xargs -0 chmod g+s 

however when fred commits git repository, group not preserved in files.

specifically in objects directory 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 in objects/14 setgid bit not set. consequently when new object added 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 95482.. file doesn't have group bar, has group fred.

i suspect when fred commited, git created new directory on-demand called objects/14 hold new object, when did unknown reason setgid bit on new 14 directory not set, though parent directory objects has setgid bit set.

if try reproduce manually:

$ su fred                          # user fred $ mkdir test1                      # create test1 dir $ sudo chgrp bar test1             # set group 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 setgid bit in new test1/test2 is preserved, when i...

$ touch test1/test2/test3 

the new file still group bar expected:

$ ls -l test1/test2 -rw-rw-r-- 1 fred bar 0 apr  8 21:36 test3 

why doesn't git seem preserve setgid bit when creates new directories in .git directory?

is there git setting can make fix this? or can explain causing this?

it turns out when specify core.sharedrepository config, git chmod()s on files creates. way, result correct despite filesystem types , mount options, except in 1 case repository owner isn't member of group it's shared with.

that bad result happens because git's chmod() appears succeed -- can see in strace -- ignores issuing user isn't authorized ask for.

so avoid weirdity, thing is

git config --unset core.sharedrepository 

(or not specify --shared @ on init) git doesn't touch filesystem's default permissions @ all. amusingly enough makes 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) /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$