Re: [PATCH 1/2] Use git_open_noatime when accessing pack data

Junio C Hamano wrote:

 (1) introduce "int git_open_ro(const char *)" to replace the current
     git_open_noatime().  The point is that the function no longer is
     about avoiding from smudging the inode metadata.  Instead, it becomes
     the preferred way for us to get a read-only fd.

[...]

We can of course do without s/git_open_noatime/git_open_ro/; and it will
make the patch much smaller.  The rename is purely a clarification of the
API and is optional.  It may make it easier to explain the name of the new
function, though.

Probably a silly question, but should all readonly open()s actually use
noatime?  Some uses for atime:

 - tmpwatch.  That one's a bit insane, anyway, but I think it might
   work because loose objects and packs are read-only.

 - mail clients.  For this case, noatime is the right thing to do ---
   git's access does mean the mail was read.

 - listing important files, as in popularity-contest.  For this,
   noatime is also the right thing to do.

Judging from these three use cases, readonly open()s to the worktree
should indeed use noatime, but open()s of .git/config, say, should
not.  Hmm.