patch: support diff data loss detection and upgrade
In worst case, generating diff in upgrade mode can be two times more expensive
than generating it in git mode directly: we may have to regenerate the whole
diff again whenever a git feature is detected. Also, the first diff attempt is
completely buffered instead of being streamed. That said, even without having
profiled it yet, I am convinced we can fast-path the upgrade mode if necessary
were it to be used in regular diff commands, and not only in mq where avoiding
data loss is worth the price.
#!/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