Re: [PATCH 3/3] completion: offer ctags symbol names for 'git log -S', '-G' and '-L:'

[Jeff King <peff@peff.net>]

On Thu, Mar 23, 2017 at 04:38:39PM +0100, SZEDER Gábor wrote:

> Just like in the case of search patterns for 'git grep', see 29eec71f2
> (completion: match ctags symbol names in grep patterns, 2011-10-21)),
> a common thing to look for using 'git log -S', '-G' and '-L:' is the
> name of a symbol.
> 
> Teach the completion for 'git log' to offer ctags symbol names after
> these options, both in stuck and in unstuck forms.

I think this makes sense and is an improvement over the status quo.

There are two gotchas with completing "-L" like this:

  1. You still have to come up with the filename yourself for "-L".

  2. The function name is actually a regex, so you can get bit when your
     function name is a subset of another.

I have a script (below) which makes this easier (and I complete its
argument using the tags file).  It's probably too gross to even go into
contrib, but I thought I'd share.

"log -S" sometimes benefits from limiting by filename, too, but it
depends what you're doing. I don't have a gross script for that. :)

-- >8 --
#!/usr/bin/env perl
if (!@ARGV) {
  print STDERR "usage: git flog [options] <function>\n";
  exit 1;
}

my $func = pop @ARGV;
my $file = get_file_from_tags($func);
my $regex = '[^A-Za-z_]' . $func . '[^A-Za-z0-9_]';
exec qw(git log), "-L:$regex:$file", @ARGV;
exit 1;

sub get_file_from_tags {
  my $token = shift;

  open(my $fh, '<', 'tags')
    or die "unable to open tags: $!\n";
  while (<$fh>) {
    chomp;

    # this isn't exactly right, as the Ex command may contain
    # embedded tabs, but it's accurate for the token and filename,
    # which come before, and probably good enough to match extension fields
    # which come after
    my @fields = split /\t/;

    next unless $fields[0] eq $token;

    # only look for functions; assumes your ctags uses the "kind"
    # extension field. Note also that some implementations write the "kind:"
    # header and some do not. This handles both.
    next unless grep { /^(kind:\s*)?f$/ } @fields;

    # there may be more, but we don't have any way of disambiguating,
    # so just return the first match
    return $fields[1];
  }

  die "unknown token: $token\n";
}
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