Re: git fetch --tags doesn't quite do what I expect

From: Junio C Hamano <junkio@cox.net>
Date: Nov 18, 2005, 20:06 UTC
Message-ID: <7v1x1diuuy.fsf@assigned-by-dhcp.cox.net>
In-Reply-To: <12c511ca0511181114jf4ca3c0p195a128fa541b8f2@mail.gmail.com>

Tony Luck <tony.luck@gmail.com> writes:

> Is this intended behaivour?  If so, the "--tags" entry on the
> git-fetch(1) man page needs a little extra text to say that
> --tags limits the fetch to only commits reachable from the
> tags.

I think both Linus (who did the initial implementation of "git fetch --tags") and I are in "tags do not matter until you care" camp, and the expected usage pattern is that you frequently do "git fetch" or "git pull", but "git fetch --tags" is done only every once in a while, just to give you known anchors to compare against or specify a known bottom for log, whatchanged and friends. The branch heads are necessary for your day to day work, the tags are less essential. That is what I mean by "tags do not matter until you care".

A tag usually points at somewhere in the commit chain leading to branch heads [*1*], and if your branch heads are up to date, "git fetch --tags" does not download anything other than the tags themselves, finds the commits they point at are already available and complete, and stops there.

Now it happens that "git fetch --tags" slurps commits you do not yet have _if_ your branch heads are behind, because git barebone Porcelain is designed to keep your object database complete (i.e. it does not just fetch and store tags under refs/tags/ without making sure you have everything they connect to). What you saw that is a side effect of the above design assumption.

I am not good at documenting things, so I'd appreciate if somebody paraphrased the above and send it back to me in a patch form to update the document ;-).

[Footnote]

*1* This is not necessarily true; tags can point at anything, and indeed v1.0rc3 tag point at another tag and junio-gpg-tag points at a freestanding blob. Even a tag pointing at a commit, as Daniel suggested in

	<Pine.LNX.4.64.0511041745480.25300@iabervon.org>

I could do the "pu" branch as a tag without exposing the actual branch. Then that tag would point at a chain of commits not connected to any branch head.