Re: [PATCH 2/2] completion: simplify ls-files filter

You didn't run the test suite, did you? ;)

First, neither 'git ls-files' nor 'git diff-index' produce quite the same order as the 'sort' utility does, e.g.:

  $ touch foo.c foo-zzz.c
  $ git add foo*
  $ git diff-index --name-only HEAD
  foo-zzz.c
  foo.c
  $ git diff-index --name-only HEAD |sort
  foo.c
  foo-zzz.c

Second, the output of 'git ls-files' is kind of "block-sorted": if you were to invoke it with the options '--cached --modified --others', then it will first list all untracked files in order, then all cached files in order, and finally all modified files in order. Note the implications:

  - A file could theoretically be listed twice, because a modified
    file is inherently cached as well.  I believe this doesn't happen
    currently, because no path completions use the combination of
    '--modified --cached', but we use a lot of options when completing
    paths for 'git status', and I haven't thought that through.

  - A directory name is repeated in two (or more) blocks, if it
    contains modified and untracked files as well.  We do use the
    combination of '--modified --others' for 'git add', and '--cached
    --others' for 'git mv', so this does happen.

Note also that there can be any number of other files between the same directory listed in two different blocks. That 'sort' that this patch is about to remove took care of this, but without that 'sort' the same directory name can be listed more than once even after 'uniq'. Consequently, the subsequent filtering of paths matching the current word to be completed might have twice as much work to do.

All this leads to the failure of an enormous test in t9902, hence my rethorical question at the beginning of my reply.

I have a short patch series collecting dust somewhere for a long while, which pulls a couple more tricks to make git-aware path completion faster, but haven't submitted it yet, because it doesn't work quite that well when filenames require quoting. Though, arguably the current version doesn't work quite that well with quoted filenames either, so... Will try to dig up those patches.