debuginstall: report the template path

extensions: print some debug info on import failure This is handy if hgext.foo exists but has a bogus "import blah": previously we just discarded the "No module named blah" error. Now at least you can see it with --debug. Not perfect, but better than nothing.

import: wrap a transaction around the whole command Now 'rollback' after 'import' is less surprising: it rolls back all of the imported changesets, not just the last one. As an extra added benefit, you don't need 'rollback -f' after 'import --bypass', which was an undesired side effect of fixing issue2998 (59e8bc22506e).. Note that this is a different take on issue963, which complained that rollback after importing multiple patches returned the working dir parent to the starting point, not to the second-last patch applied. Since we now rollback the entire import, returning the working dir to the starting point is entirely logical. So this change also undoes a732eebf1958, the fix to issue963, and updates its tests accordingly. Bottom line: rollback after import was weird before issue963, understandable since the fix for issue963, and even better now.