Fix machine-parseability of 'git log --source'

[Linus Torvalds <torvalds@linux-foundation.org>]

The space between the commit and the source attribute is not easily 
machine-parseable: if we combine --source with --parents and give a SHA1 
as a starting point, it's unnecessarily hard to see where the list of 
parents ends and the source decoration begins.

Example:
	git show --parents --source $(git rev-list HEAD)

which is admittedly contrived, but can easily happen in scripting.

So use a <tab> instead of a space as the source separator.

The other decorations didn't have this issue, because they were surrounded 
by parenthesis, so it's obvious that they aren't parent SHA1's.

It so happens that _visually_ this makes no difference for "git log 
--source", since "commit <40-char SHA1>" is 47 characters, so both a space 
and a <tab> will end up showing as a single commit. Of course, with 
'--pretty=oneline' or '--parents' or '--abbrev-commit' you'll see the 
difference.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

This is all partly because I also wish that 'gitk' would use --decorate to 
give decorations rather than look them up by hand. I'm not entirely source 
--source is useful for gitk (since it wants _all_ branches), but I do know 
that I hate knowing that

	gitk --source

just results in parse errors.

 log-tree.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/log-tree.c b/log-tree.c
index 5444f08..194ddb1 100644
--- a/log-tree.c
+++ b/log-tree.c
@@ -58,7 +58,7 @@ void show_decorations(struct rev_info *opt, struct commit *commit)
 	struct name_decoration *decoration;
 
 	if (opt->show_source && commit->util)
-		printf(" %s", (char *) commit->util);
+		printf("\t%s", (char *) commit->util);
 	if (!opt->show_decorations)
 		return;
 	decoration = lookup_decoration(&name_decoration, &commit->object);