Re: Git tag: pre-receive hook issue

On Sat, Jul 18, 2015 at 1:08 PM, Gaurav Chhabra
[off-list ref] wrote:

Thanks for the comments Junio/Jacob! Actually, the script was written
by someone before i came and the tag check was also done by my
colleague recently. I was also trying to implement the tag check
(using refs/tags which i did saw in few links online) but since my
colleague implemented this 'git describe' thing first and it looked
like it was working for few cases that we tried, so we left it as is.
Frankly, since everything 'seemed' to be working well so far, i never
really quite looked into it. Now i guess, it's time to correct it.


@Junio: From the example you gave, i could conclude the following:

1) : gitster garbage/master; git commit --allow-empty -m third
  [master d1f1360] third
  : gitster garbage/master; git describe --exact-match HEAD ;# third
  fatal: no tag exactly matches 'd1f1360b46dfde8c6f341e48ce45d761ed37e357'

quoted

Since after # third commit, no tag was applied to HEAD, so --exact-match resulted in fatal error

2)  : gitster garbage/master; git commit --allow-empty -m second
[master d1de78e] second
: gitster garbage/master; git tag -a -m 'v0.1' v0.1
: gitster garbage/master; git describe --exact-match HEAD^ ;# second
    v0.1

quoted

Since annotated tag was applied after # second commit, so --exact-match did referenced the commit as expected.

3) : gitster garbage/master; git commit --allow-empty -m initial
  [master (root-commit) b18cac2] initial
  : gitster garbage/master; git tag v0.0 ;# lightweight
  : gitster garbage/master; git describe --exact-match HEAD^^ ;# first
  fatal: no tag exactly matches 'b18cac237055d9518f9f92bb4c0a4dac825dce17'

quoted

In this case, it's a lightweight tag and i read today that by default, git describe only shows annotated tags (without --all or --tags). I think it's because of the missing option (--all or --tags) that it resulted in fatal error in this case.

Please correct me if i misunderstood any/all of the above cases.

My queries:
A) When you mentioned: "I am feeding three _commits_, not tags.", i
didn't really get what you're trying to highlight. Is it that the code
i shared 'incorrectly' uses 'git describe' command because it's
passing the commit ($new_sha1) associated with pushing of the tag
_instead_ of passing the commit id that the tag actually points to?

B) Coming to the earlier part of the code that you questioned. Thanks
for that. As i mentioned above, some guy had written it long time back
(few years). And again, since this never caused any issue, we never
looked into it. I did read a little about rev-list today but i think
i'll have to try it out on my machine to understand it well. Will read
more and then implement the check but yes, i do get an idea what
you've tried to question. Basically, for new branch or new
development, we are not really doing complete checks. Correct?

You've also mentioned that "And you check everything on that list.  Why?"

quoted

Was this comment for the portion where the code is validating commits (git rev-list $old_sha1..$new_sha1) for existing branch? If yes, then i didn't really get your concern. Can you kindly elaborate a bit?

And thanks for sharing the modified version! :)


@Jacob: You're right. If i understood correctly what Junio explained,
then what the code is doing really shouldn't make any sense at all. :)

By the way, you mentioned, "Ok, so the issue I believe is this: you're
running git describe on the local side. But the pre-receive hook
hasn't actually accepted the ref yet so git-describe on the server
will fail."

quoted

When i push a tag, then as per the output i shared, the commit id associated with my tag push is ac28ca721e67a. So if i do a "git describe --exact-match ac28ca721e67a", then

1) First of all, it shouldn't make any sense because as "git describe"
should accept _actual_ commit id and not the commit id generated for
tag push, isn't it?

git describe will attempt to describe the commit ID you pass it. But
the tag object for a "new" tag push will not get "described" because
the pre-receive hook runs before you push it.

It would help a lot if we understood exactly what you are trying to accomplish.

If you run git describe locally, it will find the annotated tag you
made. If you run this remotely during the pre-receive of the tag that
you now now pushing it will not. ie:

$git tag -a some-new-tag ac28ca721e67a
$git describe --exact-match ac28ca721e67a
<succeeds and finds "some-new-tag"
$git push origin some-new-tag
<pre-receive runs>
git describe --exact-match ac28ca721e67a
<FAILS because the "some-new-tag" hasn't actually bet put into refs yet>

See the difference here? Maybe this isn't what you are trying to do at
all? What exactly behavior do you want to not allow?

Regards,
Jake

2) If i got the above right, then shouldn't Git throw an error even on
my local machine when i'm running "git describe --exact-match
ac28ca721e67a"?

Not with my example above. But maybe I'm incorrect entirely in what
you are actually doing?

@Junio/Jacob: I think i've asked quite a number of questions above but
i will really appreciate if you could spare some time to clear these
doubts. I'm definitely going to change this junk code but i would like
to be sure that i've understood your explanations well.