sparse: clean up config signature code
Before, 0 was being used as the default signature value and we cast
the int to a string. We also handled I/O exceptions manually.
The new code uses cfs.tryread() so we always feed data into the
hasher. The empty string does hash and and should be suitable
for input into a cache key.
The changes made the code simple enough that the separate checksum
function could be inlined.
#require execbit
$ hg init
$ echo a > a
$ hg ci -Am'not executable'
adding a
$ chmod +x a
$ hg ci -m'executable'
$ hg id
79abf14474dc tip
Make sure we notice the change of mode if the cached size == -1:
$ hg rm a
$ hg revert -r 0 a
$ hg debugstate
n 0 -1 unset a
$ hg status
M a
$ hg up 0
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg id
d69afc33ff8a
$ test -x a && echo executable -- bad || echo not executable -- good
not executable -- good