"darcs get --tag" matches on a regexp. This is a very questionable
design choice. When getting from a repo with a tag you typically want
to check out a certain specific version. The probability of getting the
wrong version is high: imagine you have the two tags "1.2" and "1.2.1",
then "darcs get --tag=1.2" will select the later version 2.1.1, not
1.2. This is very error-prone. You have to remember to bracket the tag
name between ^ and $, and since the latter is (in Unix) a shell meta
character, everything has to be quoted. This is all very cumbersome.
A backward compatible solution would be some option like --exact-match,
which the user could then put in his ~/.darcs/defaults file.

It may be that if I understand well, one solution can be generated the regexp of the string/tag, say r, with 
the prefix ^ and sufix $. Ie, right now the regexp is generated of this way `mkRegex r` and I propose 
generate of this way ` mkRegex $ "^" ++ r ++ "$" ` .

But I don't full understand which may be the problem with backward compatible.

Hmm, interesting.

--tag . is a very handy darcs idiom that outlive sad to lose

Having tag behave inconsistently in get v other commands would be a pain
Having matches behave inconsistently with each other would also be bad
(otoh you could argue tag is different)

Maybe Max's flag is way forward

Or maybe darcs would issue a BTW after the fact (there are also 56 matches,
including 1.2, 1.1.2; did you mean --tag '^1.2$'?

On Friday, 28 March 2014, Alejandro Gadea <bugs@darcs.net> wrote:

>
> Alejandro Gadea <alex.aegf@gmail.com <javascript:;>> added the comment:
>
> It may be that if I understand well, one solution can be generated the
> regexp of the string/tag, say r, with
> the prefix ^ and sufix $. Ie, right now the regexp is generated of this
> way `mkRegex r` and I propose
> generate of this way ` mkRegex $ "^" ++ r ++ "$" ` .
>
> But I don't full understand which may be the problem with backward
> compatible.
>
> __________________________________
> Darcs bug tracker <bugs@darcs.net <javascript:;>>
> <http://bugs.darcs.net/issue2038>
> __________________________________
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> darcs-devel@darcs.net <javascript:;>
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>


-- 
Eric Kow <http://erickow.com>

Attachments

• unnamed

My rationale for first proposing a "non-standard" behaviour (i.e. that
darcs get --tag always does an exact match) was that currently the
command 'darcs get --tag' is not well-defined for non-unique matches. An
indication is that the manual doesn't say what happens in that case.
Indeed, the test I attached (not in standard test format, just a quick
demo) demonstrates that the result depends on the order in which patches
are applied. IMHO this is very nasty, but it is a separate issue.

The reason I walked back from my first proposal: the incompatibility is
that people (like me) work around the issue by saying: darcs get --tag
'^the-real-tag-name$'. If we were to change the meaning of --tag to be
the exact tag name then such uses, e.g. in scripts, would break.

This is why my second proposal was to add --exact switch.

Attachments

• test.sh

I really wish we could make some progress with this issue.

It may be ugly but I think the best solution is to introduce a new
option --exact-tag as an additional variant for all commands that
currently accept --tag. Then deprecate --tag (using it should issue a
warning "--tag is deprecated, you probably want to use --exact-tag") and
in the help output, move it to the advanced section, or even better,
don't document it at all.