On 12/28/2015 09:30 PM, Junio C Hamano wrote:
Mostyn Bramley-Moore <mostynb@xxxxxxxxx> writes:
git describe currently only supports glob matching with the --matches flag.
It would be useful to support regular expressions.
For consistency, this uses the same regex flags as those used by git-grep.
Some old discussion of this as a candidate feature is here, though nobody put
together a patch as far as I can see:
http://comments.gmane.org/gmane.comp.version-control.git/173873
Thanks.
I do not think it is wrong per-se to add an option to use regular
expressions instead of globs, but if we are to do so, the endgame we
aim for MUST be that we do so consistently to all the other commands
that iterate over refs and limit their output to the ones that match
given pattern (or a set of patterns), not just 'describe'.
There is one important distinction between 'git describe' and the other
commands that iterate through refs- it applies an internal search
strategy and outputs at most one match. This makes it difficult to
search for the closest matching tag that matches any item in a set of
patterns without some messy scripting (ie run multiple 'git describe'
commands, for each pattern, then figure out which result is the one you
want).
Even if we are not adding such an option to these other commands
right now (yet), we at least need to know what these commands are
(e.g. "git tag -l" and "git for-each-ref" immediately come to mind,
but there may be others), and make sure that the option names you
choose here can be used sensibly in their context. I think "tag"
and "for-each-ref" do no pattern matching against anything other
than the refnames, so it would be clear what a new --perl-regexp
option does in their contexts.
The commands that you mention produce a list of results, which can
easily be processed by an external util (eg grep itself), and might not
need similar arguments to be added.
Adding regex pattern matching to 'git describe' is just one reasonable
(IMO) solution, but there are a couple of alternatives that might suffice:
1) Add an option to print all tags, in a well-defined/useful order.
Then the results would be easy to process by an external command too.
2) Add support for multiple patterns, and print the first found item
that matches any of them.
Unlike "grep" whose sole point is to perform pattern matching, the
filtering of refs these commands do is merely a very small tweak in
the overall picture (e.g. "git tag --contains $commit -l $pattern"
does filter by matching $pattern against the refname, but that is a
small detail compared to the filtering done by the reachability with
the $commit), so I am not sure if short -E/-G/-F/-P should be given
to these commands like "grep" does, though. These commands may have
better uses for these shorter option names.
Besides 'git grep', the only regex type flag that is given a short
option seems to be -E for 'git log' and 'git rev-list'. I have no
objection to dropping the short options, or leaving only -E.
-Mostyn.
--
Mostyn Bramley-Moore
TV and Connected Devices
Opera Software ASA
mostynb@xxxxxxxxx
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