blame: use the fingerprint heuristic to match ignored lines

blame: use the fingerprint heuristic to match ignored lines

This commit integrates the fuzzy fingerprint heuristic into
guess_line_blames().

We actually make two passes.  The first pass uses the fuzzy algorithm to
find a match within the current diff chunk.  If that fails, the second
pass searches the entire parent file for the best match.

For an example of scanning the entire parent for a match, consider:

	commit-a 30) #include <sys/header_a.h>
	commit-b 31) #include <header_b.h>
	commit-c 32) #include <header_c.h>

Then commit X alphabetizes them:

	commit-X 30) #include <header_b.h>
	commit-X 31) #include <header_c.h>
	commit-X 32) #include <sys/header_a.h>

If we just check the parent's chunk (i.e. the first pass), we'd get:

	commit-b 30) #include <header_b.h>
	commit-c 31) #include <header_c.h>
	commit-X 32) #include <sys/header_a.h>

That's because commit X actually consists of two chunks: one chunk is
removing sys/header_a.h, then some context, and the second chunk is
adding sys/header_a.h.

If we scan the entire parent file, we get:

	commit-b 30) #include <header_b.h>
	commit-c 31) #include <header_c.h>
	commit-a 32) #include <sys/header_a.h>

Signed-off-by: Barret Rhoden <brho@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>