treemanifest: speed up commit using dirty flag
We currently avoid saving a treemanifest revision if it's the same as
one of it's parents. This is checked by comparing the generated text
for all three versions. Let's avoid that when possible by comparing
the nodeids for clean (not dirty) nodes.
On the Mozilla repo, this speeds up commit from 2.836s to 2.343s.
#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