todo: Curse of the headless git [PATCH]

doc/todo/headless_git_branches.mdwn

@@ -0,0 +1,56 @@
+Ikiwiki should really survive being asked to work with a git branch that has no existing commits.
+
+    mkdir iki-gittest
+    cd iki-gittest
+    GIT_DIR=barerepo.git git init
+    git clone barerepo.git srcdir
+    ikiwiki --rcs=git srcdir destdir
+
+I've fixed this initial construction case, and, based on my testing, I've also fixed the post-update executing on a new master, and ikiwiki.cgi executing on a non-existent master cases. Unfortunately these cases still generate a lot of warnings from recentchanges; I suspect a much more invasive patch would be needed to shut those up.
+
+Please commit so my users stop whining at me about having clean branches to push to, the big babies.
+
+Summary: Change three scary loud failure cases related to empty branches into three scary loud success cases.
+<pre>
+diff --git a/IkiWiki/Plugin/git.pm b/IkiWiki/Plugin/git.pm
+index cf7fbe9..5b1e334 100644
+--- a/IkiWiki/Plugin/git.pm
++++ b/IkiWiki/Plugin/git.pm
+@@ -439,10 +439,13 @@ sub git_commit_info ($;$) {
+ 
+ 	my @opts;
+ 	push @opts, "--max-count=$num" if defined $num;
++        my @raw_lines;
+ 
+-	my @raw_lines = run_or_die('git', 'log', @opts,
+-		'--pretty=raw', '--raw', '--abbrev=40', '--always', '-c',
+-		'-r', $sha1, '--', '.');
++        if (-e $config{srcdir} . "/.git/refs/heads/" . $config{gitmaster_branch}) {
++                @raw_lines = run_or_die('git', 'log', @opts,
++                        '--pretty=raw', '--raw', '--abbrev=40', '--always', '-c',
++                        '-r', $sha1, '--', '.');
++        };
+ 
+ 	my @ci;
+ 	while (my $parsed = parse_diff_tree(\@raw_lines)) {
+@@ -474,7 +477,10 @@ sub rcs_update () {
+ 	# Update working directory.
+ 
+ 	if (length $config{gitorigin_branch}) {
+-		run_or_cry('git', 'pull', '--prune', $config{gitorigin_branch});
++                run_or_cry('git', 'fetch', '--prune', $config{gitorigin_branch});
++                if (-e $config{srcdir} . '/.git/refs/remotes/' . $config{gitorigin_branch} . '/' . $config{gitmaster_branch}) {
++                        run_or_cry('git', 'merge', $config{gitorigin_branch} . '/' . $config{gitmaster_branch});
++                }
+ 	}
+ }
+ 
+@@ -559,7 +565,7 @@ sub rcs_commit_helper (@) {
+ 	# So we should ignore its exit status (hence run_or_non).
+ 	if (run_or_non('git', 'commit', '-m', $params{message}, '-q', @opts)) {
+ 		if (length $config{gitorigin_branch}) {
+-			run_or_cry('git', 'push', $config{gitorigin_branch});
++			run_or_cry('git', 'push', $config{gitorigin_branch}, $config{gitmaster_branch});
+ 		}
+ 	}
+</pre>