tests/test-impexp-branch

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

cat >findbranch.py <<EOF
import re, sys

head_re = re.compile('^#(?:(?:\\s+([A-Za-z][A-Za-z0-9_]*)(?:\\s.*)?)|(?:\\s*))$')

for line in sys.stdin:
    hmatch = head_re.match(line)
    if not hmatch:
        sys.exit(1)
    if hmatch.group(1) == 'Branch':
        sys.exit(0)
sys.exit(1)
EOF
hg init a
cd a
echo "Rev 1" >rev
hg add rev
hg commit -m "No branch."
hg branch abranch
echo "Rev  2" >rev
hg commit -m "With branch."
if hg export 0 | python ../findbranch.py; then
    echo "Export of default branch revision has Branch header" 1>&2
    exit 1
fi
if hg export 1 | python ../findbranch.py; then
    :  # Do nothing
else
    echo "Export of branch revision is missing Branch header" 1>&2
    exit 1
fi
# Make sure import still works with branch information in patches.
cd ..
hg init b
cd b
hg -R ../a export 0 | hg import -
hg -R ../a export 1 | hg import -
cd ..
rm -rf b
hg init b
cd b
hg -R ../a export 0 | hg import --exact -
hg -R ../a export 1 | hg import --exact -