mq: use fallback patch name if no alpha-numeric in summary line (
issue5025)
Before this patch, "hg qimport -r REV" fails, if the summary line of
description of REV doesn't contain any alpha-numeric bytes.
In this case, all bytes in the summary line 'title' are dropped from
'namebase' by the code path below.
namebase = re.sub('[\s\W_]+', '_', title.lower()).strip('_')
'makepatchname()' immediately returns this empty string as valid patch
name, because patch name conflicting against empty string never
exists.
Then, "hg qimport -r REV" is aborted at creation of patch file with
empty filename.
This situation isn't so rare. For example, ordinary texts in Japanese
often consist of non alpha-numeric bytes in UTF-8.
This patch makes 'makepatchname()' use fallback patch name if the
summary line of imported revision doesn't contain any alpha-numeric
bytes.