When cloning with the -r option or # url format from a tag the destination
repo most likely won't have the tag. We can save the lookup result to get to
the correct parent anyway. Similar to issue1306, but for tags.
- Example: "hg tag -r 42 build-25 beta-1" will add tags build-25 and beta-1
for rev 42.
- The deprecated and undocumented usage "hg tag arg1 arg2" used to emit a
warning, then add tag arg1 for rev arg2 (equivalent to "hg tag -r arg2 arg1").
It will now add tags arg1 and arg2 for the current revision.
- If one tag triggers an error, no tags are added/removed (all or nothing).
Some systems show "Thu Jan 01" instead of "Thu Jan 1", which breaks tests.
Using "1000000" yields "Mon Jan 12 13:46:40 1970", which looks the same on
all systems.