Re: [PATCH] config option core.showroot to enable showing the diff of the root commit

From: Junio C Hamano <junkio@cox.net>
Date: Nov 24, 2006, 08:54 UTC
Message-ID: <7vlkm1cjht.fsf@assigned-by-dhcp.cox.net>
In-Reply-To: <slrnemd98k.a3v.Peter.B.Baumann@xp.machine.xx>

Peter Baumann <Peter.B.Baumann@stud.informatik.uni-erlangen.de> writes:

> One question, what's the difference between git-log -p and
> git-whatchanged -p?
> ...
> As you can see, the root commit isn't shown. Is this intentional?

Some historical background.

The traditional command do do log-minded things was whatchanged and it was implemented as

	git rev-list $revision_args -- $path_limits |
        git diff-tree --stdin --pretty -r $format_args

and whatchanged did not give --root to diff-tree by default. And 'diff-tree' does not show --pretty logs when there is no diff to be shown (which still is true today and is a useful behaviour), hence no mention of the root commit.

On the other hand, "git-log" traditionally looked like this:

	git rev-list --pretty $revision_args

Back then, there was no path_limits nor even diff options to it.

Later, Linus (with help from others) made the revision walk machinery as callable inside programs other than "rev-list", eliminating the need to pipe rev-list into diff-tree to perform log-minded things. That enriched what "git log" can do, and mostly made "whatchanged" a redundant command. As you may have noticed, there isn't much difference between these two commands in builtin-log.c; their differences are solely what default options for diff and revision machinery are used and are meant to match the traditional behaviour of these commands.

So there shouldn't be any differences, really, when you override their defaults with the likes of -p.

Honestly speaking, I do not think there was _any_ consciously designed intention to handle root commits, either to make these commands behave identically or differently; regarding parentless commits, they just behave the way they happen to behave, because root commits were not something either Linus nor I were interested in.

Given the recent discussion, however, the intention now should be that Porcelain level commands should default to do --root (i.e. when asked to do "diff" to show how a commit without a parent differs from its nonexistent parent, show diff with emptiness).