subrepo: add partial diff support for git subrepos So far, git subrepositories were silently ignored for diffs. This patch adds support for git subrepositories, with the remark that --include and --exclude are not supported. If --include or --exclude are used, the subrepo is ignored.

subrepo: extend git version check to 3 digits This allows more flexibility when a version check is required. Some git features are introduced in a version where only the 3rd digit changes.

subrepo: move git version check into a separate method This allows checking the git version in other methods, instead of only being able to check if the version is ok or not.

rebase: show a note for updated mq patches It deserves more than a debug message. Show a note like: updating mq patch p0.patch to 5:9ecc820b1737 The message could also refer to "qrefresh" instead. Same same.