Both 'git blame -L' and 'git log -L' parse the same style
of line number arguments, so put the 'parse_loc' function
to line.c and export it.
The caller of parse_loc should provide a callback function
which is used to calculate the start position of the nth line.
Other parts such as regexp search, line number parsing are
abstracted and re-used.
Note that, we can use '$' to specify the last line of a file.
Signed-off-by: Bo Yang <struggleyb.nku@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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