trydiff: remove unused argument to diffline() Now that diffline no longer knows about copies/renames, it only needs one argument for the path.

trydiff: move git-header code out of diffline function This collects more of the code for writing git headers in a single place and makes diffline() close on a few variables less.

_fm1readmarkers: generate list in C This moves perfloadmarkers from ! result: 63866 ! wall 0.239217 comb 0.250000 user 0.240000 sys 0.010000 (best of 42) to ! result: 63866 ! wall 0.218795 comb 0.210000 user 0.210000 sys 0.000000 (best of 46)

obsolete: use parsers.fm1readmarker if it exists for a ~38% perf win This moves perfloadmarkers on my linux workstation (63494 markers from mpm, crew, and myself) performance from ! wall 0.357657 comb 0.360000 user 0.350000 sys 0.010000 (best of 28) to ! wall 0.222345 comb 0.220000 user 0.210000 sys 0.010000 (best of 41) which is a pretty good improvement. On my BSD machine, which is ancient and slow, before: ! wall 3.584964 comb 3.578125 user 3.539062 sys 0.039062 (best of 3) after: ! wall 2.267974 comb 2.265625 user 2.195312 sys 0.070312 (best of 5) I feel like we could do better by moving the whole generator function into C, but I didn't want to tackle that right away.

parsers: add fm1readmarker This lets us do most of the interesting work of parsing obsolete markers in C, which should provide significant time savings. Thanks to Martin von Zweigbergk for some cleanups on this code.

util: add getbefloat64 As far as I can tell, this is wrong. double's format isn't strictly specified in the C standard, but the wikipedia article implies that platforms implementing optional Annex F "IEC 60559 floating-point arithmetic" will work correctly. My local C experts believe doing *((double *) &t) is a strict aliasing violation, and that using a union is also one. Doing memcpy appears to be the least-undefined behavior possible.