Re: git diff-tree against the root commit
- From
Linus Torvalds <torvalds@linux-foundation.org>
- Date
- Nov 7, 2010, 17:23 UTC
- Message-ID
- <AANLkTimiyFhggBvK-AGqRnMXta65rEJvJSeQ+QGOnZWp@mail.gmail.com>
- In-Reply-To
- <4CD68662.4060709@gmx.de>
On Sun, Nov 7, 2010 at 2:58 AM, Christoph Mallon <christoph.mallon@gmx.de> wrote:
Show 10 quoted lines
> On 29.10.2010 08:13, Joshua Jensen wrote: >> I am mirroring a Git repository into another SCM. I am using 'git diff-tree' to tell me what changes I need to make to the other SCM. >> >> Today, I attempted to mirror a new submodule. 'git diff-tree' reported two SHAs... 0000000000000000000000000000000000000000 and the revision the submodule currently resides at. I attempted to run a 'git diff-tree' within the submodule for the all zero SHA and the revision specified, but apparently, 0000000000000000000000000000000000000000 does not really represent the root commit and does not work. I then discovered the --root option, but that doesn't seem to give me the complete file list either. >> >> 'git diff-tree' has been working great for everything else, but I really need a root commit diff-tree listing for proper automation. >> >> What are my options? > > Diff against the empty tree.
That works, but it's a bit too technical.
The traditional way to do it is to just
git diff-tree --root <commit>
where the magic "--root" option is just the flag to say "I want to see the root as a diff too". The reason it isn't the default is historical: since git started out for the kernel, and since the root is an import from another tree, showing the root as a patch was annoying.
You have to realize that back in the original coding days (when git read-tree was introduced), it was meant for very basic scripting. What is now "git log -p" used to be basically
git-rev-list $(cat .git/HEAD) | git-diff-tree --stdin
and with the target being the kernel, the default of not showing that first commit was a sane one (and going back even further, git-diff-tree really only worked on trees, so you had to give explicit beginning and end points).
Of course, by the time we actually had a "git log" command, I think that default had already changed. But it still explains why there is a separate option to show the root commit with a patch.
Linus