Re: performance problem: "git commit filename"

On Sat, 2008-01-12 at 17:46 -0800, Linus Torvalds wrote:

HOWEVER. When that logic was converted from that shell-script into a 
builtin-commit.c, that conversion was not done correctly. The old "git 
read-tree -i -m" was not translated as a "unpack_trees()" call, but as 
this in prepare_index():

	discard_cache()
	..
	tree = parse_tree_indirect(head_sha1);
	..
	read_tree(tree, 0, NULL)

which is very wrong, because it replaces the old index entirely, and 
doesn't do that stat information merging.

As a result, the index that is created by read-tree is totally bogus in 
the stat cache, and yes, everything will have to be re-computed.

Kristian?

Sorry for being late to the game, and yes, it's a bug I introduced with
the rewrite.  When doing the rewrite I was a bit puzzled by the

  git-read-tree --index-output="$TMP_INDEX" -i -m HEAD

part of the shell script.  I carried a FIXME around in the patch for a
while, as can be seen here:

  http://marc.info/?l=git&m=118478660425992&w=2

since I couldn't figure out what the difference in behavior was between
just using read_tree(), which did exactly what I wanted and the more
complicated unpack_tree().  I guess it fell through the cracks,
especially since it never caused the test suite to fail :/

Kristian