filepath.Clean shows up in profiles as a hot spot, and there seem to be
many redundant calls, particularly in ignorelist handling. We can avoid
these redundant calls by pre-cleaning entries in the ignore list, and
providing fast paths when we know we're already dealing with a cleaned
candidate path.
Before:
580ms 3.03% 72.35% 590ms 3.08% path/filepath.(*lazybuf).append (inline)
390ms 2.03% 74.39% 990ms 5.16% path/filepath.Clean
After:
0.13s 0.69% 84.01% 0.17s 0.91% path/filepath.(*lazybuf).append (inline)
0.13s 0.69% 84.70% 0.31s 1.65% path/filepath.Clean
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