I agree, the git config option seems best.
However, caution: it is called "--shared" not "--share". Also, from the man page:
--shared[=(false|true|umask|group|all|world|everybody|0xxx)]
Specify that the git repository is to be shared amongst several users. This allows users belonging to the same group to push into that repository. When
specified, the config variable "core.sharedRepository" is set so that files and directories under $GIT_DIR are created with the requested permissions.
When not specified, git will use permissions reported by umask(2).
The option can have the following values, defaulting to group if no value is given:
· umask (or false): Use permissions reported by umask(2). The default, when --shared is not specified.
· group (or true): Make the repository group-writable, (and g+sx, since the git group may be not the primary group of all users). This is used to loosen
the permissions of an otherwise safe umask(2) value. Note that the umask still applies to the other permission bits (e.g. if umask is 0022, using group
will not remove read privileges from other (non-group) users). See 0xxx for how to exactly specify the repository permissions.
· all (or world or everybody): Same as group, but make the repository readable by all users.
· 0xxx: 0xxx is an octal number and each file will have mode 0xxx. 0xxx will override users' umask(2) value (and not only loosen permissions as group
and all does). 0640 will create a repository which is group-readable, but not group-writable or accessible to others. 0660 will create a repo that is
readable and writable to the current user and group, but inaccessible to others.
Therefore, it does not seem that "2775" is an applicable mode. I suggest we simply use "--shared=group", since that is our intent (it will always be clearer to write an intent with a word than using obscure octal modes).