doc: translate from :hg:`help config` to a valid link to hgrc.5.html
Before this patch, ":hg:`help config`" in online help text is
translated to a link to "hg.1.html#config" in HTML, even though actual
"hg help config" shows not help for "hg config" command but "config"
help topic, and all of current ":hg:`help config`" expects the latter.
This patch translates from ":hg:`help config`" in online help text to
a link to "hgrc.5.html" in HTML as expected.
This patch also allows ":hg:`help -c COMMAND`" style to link
"hg.1.html#COMMAND" for readability.
$ hg init
$ touch unknown
$ touch a
$ hg add a
$ hg ci -m "1"
$ touch b
$ hg add b
$ hg ci -m "2"
Should show unknown
$ hg status
? unknown
$ hg revert -r 0 --all
removing b
Should show unknown and b removed
$ hg status
R b
? unknown
Should show a and unknown
$ ls
a
unknown