fix myers divide: properly trigger division on single midpoints

add test012 test010 has a weird failure to find a good diff. This new test, when setting the permitted_state_size = 100, gives a shorter failure that test010, to allow easier debugging.

debug: myers divide: log nr of identical lines slid over

fix diff_algo_myers_divide When forwards and backwards traversals meet, the endpoints of the mid-snake are not the two points in kd_forward and kd_backward, but rather the section that was slid (if any) of the current forward/backward traversal only. For example: o-o-o | | o A | \ o o \ M |\ o o-o-o | | | o o X \ o \ o \ o The backward traversal reached M from the bottom and slid upwards. The forward traversal already reached X, which is not a straight line from M anymore, so picking a mid-snake from M to X would yield a mistake. The correct mid-snake is between M and A. M is where the bottom traversal hit the diagonal that the forwards traversal has already passed, and A is what it reaches when sliding up identical lines.

debug: myers graph dump tweaks In debug output: fix some indents, fix printing of max state size, in myers graph, limit x axis labels to 2 digits, print colored markers of current myers graph positions, also print myers-divide positions in myers graph.

.gitignore: gmon.out

comment tweak

remove code dup of diff_main() invocation for plain vs unidiff

add test010, test011

Only print (unified) header in unified format.

Remove unused `arbitrary_info'.

diff_divide_myers_forward(): less indent by 'continue'

diff_output_unidiff(): less indent by 'continue'

Compat goo for gmake/glibc/Linux

Kill unused variables

Fix macro diff_atom_*idx return value types The macros sometimes returned unsigned int (atoms.len) or long int ((ATOM) - head). Make that always unsigned int, with some range checks against negative values.

diff.c: move two #include to the top

set myers fallback to myers_divide

linux_Makefile: gprof

patience: reduce sections by swallowing identical lines before LCS

move struct range defs to diff_main.h (prep for upcoming patch)

lib/linux_Makefile: -O3

debug: dump at most 42 lines

debug: dont dump too large myers graphs

dont escape tabs in text output