workingctx: correctly compute the flag for noexec filesystems+merge
This bug happens if the filesystem doesn't support exec-bit, during merges,
for example in 24ed7a541f23 on the hg repo.
If f is not in p1, but is in p2 and has the x-bit in p2, since the dirstate is
based on p1, and the FS doesn't support the exec-bit, the dirstate can't
"guess" the right bit.
We instead fix it in workingcontext.flags()/manifest.
#!/bin/sh
# test branch selection options
hg init branch
cd branch
hg branch a
echo a > foo
hg ci -d '0 0' -Ama
echo a2 > foo
hg ci -d '0 0' -ma2
hg up 0
hg branch c
echo c > foo
hg ci -d '0 0' -mc
cd ..
hg clone -r 0 branch branch2
cd branch2
hg up 0
hg branch b
echo b > foo
hg ci -d '0 0' -mb
hg up 0
hg branch -f b
echo b2 > foo
hg ci -d '0 0' -mb2
echo in rev c branch a
hg in -qr c ../branch#a
hg in -qr c -b a
echo out branch .
hg out -q ../branch#.
hg out -q -b .
echo clone branch b
cd ..
hg clone branch2#b branch3
hg -q -R branch3 heads b
hg -q -R branch3 parents
rm -rf branch3
echo clone rev a branch b
hg clone -r a branch2#b branch3
hg -q -R branch3 heads b
hg -q -R branch3 parents
rm -rf branch3