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

[Junio C Hamano <junkio@cox.net>]

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.