On Tue, Nov 15, 2016 at 12:33:04PM -0500, Matt McCutchen wrote: > On Tue, 2016-11-15 at 12:06 -0500, Jeff King wrote: > > - when an object write is optimized out because we already have the > > object, git will update the mtime on the file (loose object or > > packfile) to freshen it > > FWIW, I am not seeing this happen when I do "git read-tree --prefix" > followed by "git write-tree" using the current master (3ab2281). See > the attached test script. The optimization I'm thinking about is the one from write_sha1_file(), which learned to freshen in 33d4221c7 (write_sha1_file: freshen existing objects, 2014-10-15). I suspect the issue is that read-tree populates the cache-tree index extension, and then write-tree omits the object write before it even gets to write_sha1_file(). The solution is that it should probably be calling one of the freshen() functions (possibly just replacing has_sha1_file() with check_and_freshen(), but I haven't looked). I'd definitely welcome patches in this area. > OK. I'll write a patch to add a summary of this information to the > git-gc man page. Sounds like a good idea. Thanks. -Peff