[PATCHv2 11/14] completion: let 'for-each-ref' sort remote branches for 'checkout' DWIMery

When listing unique remote branches for 'git checkout's tracking DWIMery, __git_refs() runs the classic '... |sort |uniq -u' pattern to filter out duplicate remote branches.

Let 'git for-each-ref' do the sorting, sparing the overhead of fork()+exec()ing 'sort' and a stage in the pipeline where potentially relatively large amount of data can be passed between two subsequent pipeline stages.

This speeds up refs completion for 'git checkout' a bit when a lot of remote branches match the current word to be completed. Listing a single local and 100k remote branches, all packed, best of five:

  On Linux, before:

    $ time __git_complete_refs --track

    real    0m1.856s
    user    0m1.816s
    sys     0m0.060s

  After:

    real    0m1.550s
    user    0m1.512s
    sys     0m0.060s

  On Windows, before:

    real    0m3.128s
    user    0m2.155s
    sys     0m0.183s

  After:

    real    0m2.781s
    user    0m1.826s
    sys     0m0.136s

Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com>
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 contrib/completion/git-completion.bash | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)