convert: add copyright and license headers to back-ends

Reproduce crash where synthetic revs break merge detection (issue1578). (The fix for this was committed as 9bbcfa898cd3.) Slightly edited by Patrick Mezard <pmezard@gmail.com>

convert/svn: ignore composite tags Tools like cvs2svn generate tags made of files coming from different revisions from different branches. This is not supported by Mercurial, and it slows down the conversion a lot. Ignore them. See bacula@4082 for a sample.

Merge with crew-stable

convert/svn: keep latest and not oldest tag value

Don't use sed -r; instead use old-style regexp Rev d895158fe8af introduced some sed -r tests, but -r is only available on GNU sed, while BSD sed uses -E. Better to use old-style regular expressions, that way the tests work on all sed variants.

localrepo: Refactor var names in filecommit to improve readability.

merge with crew-stable I pushed the dd1b47e17d7e to crew before realizing that it would also be suitable for crew-stable, hence the double changeset.

Fix typeerror when specifying both --rebase and --pull

Fix typeerror when specifying both --rebase and --pull

coal, paper: omit unneeded #l1 anchor in links

localrepo: corrected outdated comment

localrepo: fixed typos in comments

help: document nonempty template filter.

webcommands: move nonempty logic from JavaScript to Python This avoids hard-coding the '(none)' string in the JavaScript for each style and avoids the {nonexisting|nonempty} hack which only works since the template system don't complain about undefined variables.

hgweb: use "nonempty" filter in templates for the changelog message At least subversion allows empty commit logs which, after conversion, show up as empty fields in hgweb and don't allow selecting the changeset. Using "nonempty" as filter, "(none)" is used to get clickable links for empty commit messages.