posix: don't compare atime when determining if a file has changed
A file's atime might change even if the file itself doesn't change. This might
cause us to invalidate caches more often than necessary.
Before this change, hg add often resulted in the dirstate being parsed twice
on systems that track atime. After this change, it is only parsed once. For a
repository with over 180,000 files, this speeds up hg add from 1.2 seconds to
1.0.
#!/usr/bin/env python
__doc__ = """Same as `echo a >> b`, but ensures a changed mtime of b.
Without this svn will not detect workspace changes."""
import sys, os
text = sys.argv[1]
fname = sys.argv[2]
f = open(fname, "ab")
try:
before = os.fstat(f.fileno()).st_mtime
f.write(text)
f.write("\n")
finally:
f.close()
inc = 1
now = os.stat(fname).st_mtime
while now == before:
t = now + inc
inc += 1
os.utime(fname, (t, t))
now = os.stat(fname).st_mtime