describe --contains: default to HEAD when no commit-ish is given

'git describe --contains' doesn't default to HEAD when no commit is given, and it doesn't produce any output, not even an error: ~/src/git ((v2.5.0))$ ./git describe --contains ~/src/git ((v2.5.0))$ ./git describe --contains HEAD v2.5.0^0 Unlike other 'git describe' options, the '--contains' code path is implemented by calling 'name-rev' with a bunch of options plus all the commit-ishes that were passed to 'git describe'. If no commit-ish was present, then 'name-rev' got invoked with none, which then leads to the behavior illustrated above. Porcelain commands usually default to HEAD when no commit-ish is given, and 'git describe' already does so in all other cases, so it should do so with '--contains' as well. Pass HEAD to 'name-rev' when no commit-ish is given on the command line to make '--contains' behave consistently with other 'git describe' options. While at it, use argv_array_pushv() instead of the loop to pass commit-ishes to 'git name-rev'. 'git describe's short help already indicates that the commit-ish is optional, but the synopsis in the man page doesn't, so update it accordingly as well. Signed-off-by: SZEDER Gábor <szeder@ira.uka.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>