convert: add a mode where mercurial_sink skips empty revisions. The getchanges function of some converter_source classes can return some false positives. I.e. they sometimes claim that a file "foo" was changed in some revision, even though its contents are still the same. convert_svn is particularly bad, but I think this can also happen with convert_cvs and, at least in theory, with mercurial_source. For regular conversions this is not really a problem - as long as getfile returns the right contents, we'll get a converted revision with the right contents. But when we use --filemap, this could lead to superfluous revisions being converted. Instead of fixing every converter_source, I decided to change mercurial_sink to work around this problem. When --filemap is used, we're interested only in revisions that touch some specific files. If a revision doesn't change any of these files, then we're not interested in it (at least for revisions with a single parent; merges are special). For mercurial_sink, we abuse this property and rollback a commit if the manifest text hasn't changed. This avoids duplicating the logic from localrepo.filecommit to detect unchanged files.

#!/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