Someone has reported to me a couple of examples which appear to be bugs in using
--from-tag=REGEXP, but since the manual doesn't explain what kind of regexps
darcs uses, I don't know if it is a bug or a misunderstanding of the regex syntax.

On Fri, May 04, 2007 at 02:24:35AM +0000, Zooko wrote:
> Someone has reported to me a couple of examples which appear to be bugs in using
> --from-tag=REGEXP, but since the manual doesn't explain what kind of regexps
> darcs uses, I don't know if it is a bug or a misunderstanding of the regex syntax.

I'm not sure what kind of regexp.  We use the haskell standard library
Text.Regex, I believe, so if it's documented there, then that's what we're
using.

A good way to test regexp behavior would be to use darcs changes --tags,
which allow you to see all the tags that match the regexp.  It's possible
that more than one tag is matching and that's causing confusion.
-- 
David Roundy
Department of Physics
Oregon State University

Here's a comment from a programmer:

"(the original goal was to use release tags that lacked the 'allmydata-tahoe-'
prefix, but it turns out to be more efficient to keep it in, because I can't get
'darcs changes --from-tag=' to accept real regexps)"

http://allmydata.org/trac/tahoe/browser/misc/make-version.py

http://www.haskell.org/ghc/docs/latest/html/libraries/regex-compat/Text-Regex.html

"Makes a regular expression with the default options (multi-line,
case-sensitive). The syntax of regular expressions is otherwise that of egrep
(i.e. POSIX "extended" regular expressions)."

Brian: are those not "real" regular expressions?  Or does darcs --changes not
actually match egrep?

See also several alternate (?) regex libraries for Haskell:

http://hackage.haskell.org/packages/archive/pkg-list.html

Are you sure it's not one of these confusing situations where you have to escape
the backslashes so that darcs really does see them as backslashes and not
something else?

The darcs manual states:

"The --patch and --tag forms simply take (POSIX extended, aka egrep) regular
expressions and match them against tag and patch names"

Please let us know if there is anything we can do to improve this.  Otherwise,
resolving.  Thanks!