Correct optimization from 3464f5e77f34; add a test.
If there are two (or more) heads that point to the same .hgtags
node, we can safely skip parsing the file in all but the last head.
(In 3464f5e77f34, we were parsing the file in the first head and
skipping all the others.)
#!/bin/sh
hg init a
cd a
echo start > start
hg ci -Amstart -d '0 0'
echo new > new
hg ci -Amnew -d '0 0'
echo '% new file'
hg diff --git -r 0
hg cp new copy
hg ci -mcopy -d '0 0'
echo '% copy'
hg diff --git -r 1:tip
hg mv copy rename
hg ci -mrename -d '0 0'
echo '% rename'
hg diff --git -r 2:tip
hg rm rename
hg ci -mdelete -d '0 0'
echo '% delete'
hg diff --git -r 3:tip
cat > src <<EOF
1
2
3
4
5
EOF
hg ci -Amsrc -d '0 0'
chmod +x src
hg ci -munexec -d '0 0'
echo '% chmod 644'
hg diff --git -r 5:tip
hg mv src dst
chmod -x dst
echo a >> dst
hg ci -mrenamemod -d '0 0'
echo '% rename+mod+chmod'
hg diff --git -r 6:tip
echo '% nonexistent in tip+chmod'
hg diff --git -r 5:6
echo '% binary diff'
cp $TESTDIR/binfile.bin .
hg add binfile.bin
hg diff --git > b.diff
cat b.diff
echo '% import binary diff'
hg revert binfile.bin
rm binfile.bin
hg import -mfoo b.diff
cmp binfile.bin $TESTDIR/binfile.bin