Severity: minor
Tags: patch

Further to https://bugs.gnu.org/64019#14, I attach a patch which tweaks
four redundant or seemingly mistyped instances of \(:?...\), i.e. a
numbered group starting with an optional colon in place of the likelier
shy group.

CCing:
- Alan to review the change to c-or-c++-mode--regexp
  (along with its clone c-ts-mode--c-or-c++-regexp)
- Dmitry to review the change in vc-git
- Paul for any comments on the time handling in vc-git-annotate-time

In vc-git-annotate-time, the mistyped group added in [1] throws off the
match string indices that are later passed to encode-time: by my reading
the hour argument by chance continues to be specified correctly, but the
minutes argument receives the number of hours, the seconds argument the
number of minutes, and the timezone argument the number of seconds.

[1]: Display shorter dates in Git annotate output
576fba5f58d 2015-05-17 02:47:17 +0300
https://git.sv.gnu.org/cgit/emacs.git/commit/?id=576fba5f58d

Even after correcting the shy group, the timezone parsing doesn't seem
right to me: encode-time expects a UTC offset in seconds, but is passed
e.g. (string-to-number "+0100")=100s instead of the expected 1hr=3600s.

IMO there is another minor issue with the regexp towards its end:

  \([-+0-9]+\) *[0-9]+

The trailing line number should be separated from the preceding
timestamp by at least one space.  So, the optional space would ideally
precede rather than follow the optional time+zone components.

The patch fixes this and the match/timezone handling by splitting the
datetime string into only three components (date, time, zone) and
delegating to iso8601-parse.