RE: Any way to get complete diff up to a tag?

From: Linus Torvalds <torvalds@linux-foundation.org>
Date: May 6, 2010, 17:08 UTC
Message-ID: <alpine.LFD.2.00.1005060955000.901@i5.linux-foundation.org>
In-Reply-To: <A612847CFE53224C91B23E3A5B48BAC74482E50F03@xmail3.se.axis.com>

On Thu, 6 May 2010, Peter Kjellerstedt wrote:

Show 6 quoted lines

> 
> Since the 4b825dc642cb6eb9a060e54bf8d69288fbee4904 SHA1 is somewhat
> cumbersome to remember, wouldn't it be an idea to give it some kind 
> of alias or mnemonic? E.g., something like @~ (or some other mix of 
> odd characters which do not clash with all the other similar 
> constructs already used for references).

Well, you don't strictly speaking have to "remember" it, you can always just re-generate it. The most straightforward way to do that is probably

	git hash-object -t tree --stdin < /dev/null

although I admit that maybe we could have some syntax for "git diff" that would do the "diff against empty tree" automatically. It does seem to be conceptually a reasonable thing to do.

For example, right now if you give "git diff" a single SHA1, it will work against the working tree. Except if you add "--cached", to say that you want the diff against the index. I don't think it would be in any way _wrong_ to make "--root" mean that you want it against an empty tree.

[ We already accept "--root", but it has no meaning for "git diff" with a 
  single SHA1. It matters for showing the root commit for 'git-diff-tree'.

  And means something totally different for git-format-patch ]

So we certainly _could_ do something like

	git diff --root <treeish>

and make it do what you want. That said, the "empty tree" thing works for all versions of git (well, some older versions of git need the actual object, but you could always use "-w" on that git-hash-object command line, and then it really should work for every git version).

			Linus