revset: document the regular expression support for tag(name)

This has been supported since 20f55613fb2a, in 2.3.

--HG--
branch : stable
hg: use "os.path.join()" to join path components which may be empty (issue4203)

Changset 2d0ab571b822 rewriting "hg.copystore()" with vfs uses
'dstbase + "/lock"' instead of "os.path.join()", because target files
given from "store.copyfiles()" already uses "/" as path separator

But in the repository using revlog format 0, "dstbase" becomes empty
("data" directory is located under ".hg" directly), and 'dstbase +
"/lock"' is treated as "/lock": in almost all cases, write access to
"/lock" causes "permission denied".

This patch uses "os.path.join()" to join path components which may be
empty in "hg.copystore()".

--HG--
branch : stable
dispatch: only do __import__(debugger) when a debugger is requested

When having ui.debugger=somedebugger in one's ~/.hgrc, this then
somedebugger would be imported for every hg command. With this patch,
this import only happens if the --debugger parameter is passed.

--HG--
branch : stable
extra : rebase_source : 1b72ba0a6e8cc9dfc7f1d940d997b6fb854432fa