From: Linus Torvalds Date: Sun, 07 Nov 2010 17:23:25 GMT Subject: Re: git diff-tree against the root commit Message-ID: In-Reply-To: <4CD68662.4060709@gmx.de> On Sun, Nov 7, 2010 at 2:58 AM, Christoph Mallon wrote: > 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 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