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 parents command
hg init repo
cd repo
echo % no working directory
hg parents
echo a > a
echo b > b
hg ci -Amab -d '0 0'
echo a >> a
hg ci -Ama -d '1 0'
echo b >> b
hg ci -Amb -d '2 0'
echo c > c
hg ci -Amc -d '3 0'
hg up -C 1
echo d > c
hg ci -Amc2 -d '4 0'
hg up -C 3
echo % hg parents
hg parents
echo % hg parents a
hg parents a
echo % hg parents c, single revision
hg parents c
echo % hg parents -r 3 c
hg parents -r 3 c
echo % hg parents -r 2
hg parents -r 2
echo % hg parents -r 2 a
hg parents -r 2 a
echo % hg parents -r 2 ../a
hg parents -r 2 ../a
echo '% cd dir; hg parents -r 2 ../a'
mkdir dir
cd dir
hg parents -r 2 ../a
echo '% hg parents -r 2 path:a'
hg parents -r 2 path:a
echo '% hg parents -r 2 glob:a'
cd ..
hg parents -r 2 glob:a
echo % merge working dir with 2 parents, hg parents c
HGMERGE=true hg merge
hg parents c
echo % merge working dir with 1 parent, hg parents
hg up -C 2
HGMERGE=true hg merge -r 4
hg parents
echo % merge working dir with 1 parent, hg parents c
hg parents c
true