patchFix `git rev-list --show-notes HEAD` when there are no notes

diff --git a/notes.c b/notes.c
index df08209..24a335a 100644
--- a/notes.c
+++ b/notes.c
@@ -1266,7 +1266,10 @@ void format_display_notes(const unsigned char *object_sha1,
 			  struct strbuf *sb, const char *output_encoding, int raw)
 {
 	int i;
-	assert(display_notes_trees);
+
+	if (!display_notes_trees)
+		return;
+
 	for (i = 0; display_notes_trees[i]; i++)
 		format_note(display_notes_trees[i], object_sha1, sb,
 			    output_encoding, raw);

diff --git a/builtin/rev-list.c b/builtin/rev-list.c
index ff84a82..fc73a6f 100644
--- a/builtin/rev-list.c
+++ b/builtin/rev-list.c
@@ -279,6 +279,7 @@ int cmd_rev_list(int argc, const char **argv, const char *prefix)
 	int bisect_show_vars = 0;
 	int bisect_find_all = 0;
 	int use_bitmap_index = 0;
+	struct userformat_want w;
 
 	git_config(git_default_config, NULL);
 	init_revisions(&revs, prefix);
@@ -349,6 +350,14 @@ int cmd_rev_list(int argc, const char **argv, const char *prefix)
 	    revs.diff)
 		usage(rev_list_usage);
 
+	memset(&w, 0, sizeof(w));
+	userformat_find_requirements(NULL, &w);
+
+	if (!revs.show_notes_given && w.notes)
+		revs.show_notes = 1;
+	if (revs.show_notes)
+		init_display_notes(&revs.notes_opt);
+
 	save_commit_buffer = (revs.verbose_header ||
 			      revs.grep_filter.pattern_list ||
 			      revs.grep_filter.header_list);

but it looks like that is not enough to convince the pretty-printer to
actually show notes (I suspect we need something like the
pretty_ctx->notes_message setup that is in show_log()).

I don't know how deeply anybody _cares_ about showing notes via
rev-list. It has clearly never worked. But rather than silently
accepting --show-notes (and not showing any notes!), perhaps we should
tell the user that it does not work. Likewise, the "%N" --format
specifier never expands in rev-list, and should probably be removed from
the rev-list documentation.

Although...

> Reported in https://github.com/msysgit/git/issues/363.

After reading your subject, I wondered why "git rev-list --show-notes
HEAD" did not crash for me (whether or not I had notes). But the key
element from that issue is the addition of "--grep", which is what
triggers us to actually look at the notes (since rev-list otherwise does
not support displaying them). And that _does_ work with my patch above.
So perhaps that is useful, though again, it has never worked in the
past (and with your patch, it would silently return no results, whether
the grep matched or not).

Of course it's a terrible interface to make "--show-notes --grep" grep
the notes, but not actually _show_ them. :-/

> diff --git a/notes.c b/notes.c
> index df08209..24a335a 100644
> --- a/notes.c
> +++ b/notes.c
> @@ -1266,7 +1266,10 @@ void format_display_notes(const unsigned char *object_sha1,
>  			  struct strbuf *sb, const char *output_encoding, int raw)
>  {
>  	int i;
> -	assert(display_notes_trees);
> +
> +	if (!display_notes_trees)
> +		return;
> +

So I'm not really in favor of this approach, but if we do go that route,
the comment above the declaration of format_display_notes needs to be
updated.

-Peff

Documentation/pretty-formats.txt, Documentation/pretty-options.txt, Documentation/rev-list-options.txt, builtin/rev-list.c

diff --git a/Documentation/pretty-formats.txt b/Documentation/pretty-formats.txt
index dc865cb..671cebd 100644
--- a/Documentation/pretty-formats.txt
+++ b/Documentation/pretty-formats.txt
@@ -139,7 +139,9 @@ The placeholders are:
 - '%f': sanitized subject line, suitable for a filename
 - '%b': body
 - '%B': raw body (unwrapped subject and body)
+ifndef::git-rev-list[]
 - '%N': commit notes
+endif::git-rev-list[]
 - '%GG': raw verification message from GPG for a signed commit
 - '%G?': show "G" for a Good signature, "B" for a Bad signature, "U" for a good,
   untrusted signature and "N" for no signature
diff --git a/Documentation/pretty-options.txt b/Documentation/pretty-options.txt
index 642af6e..8d6c5ce 100644
--- a/Documentation/pretty-options.txt
+++ b/Documentation/pretty-options.txt
@@ -42,6 +42,7 @@ people using 80-column terminals.
 	verbatim; this means that invalid sequences in the original
 	commit may be copied to the output.
 
+ifndef::git-rev-list[]
 --notes[=<ref>]::
 	Show the notes (see linkgit:git-notes[1]) that annotate the
 	commit, when showing the commit log message.  This is the default
@@ -73,6 +74,7 @@ being displayed. Examples: "--notes=foo" will show only notes from
 --[no-]standard-notes::
 	These options are deprecated. Use the above --notes/--no-notes
 	options instead.
+endif::git-rev-list[]
 
 --show-signature::
 	Check the validity of a signed commit object by passing the signature
diff --git a/Documentation/rev-list-options.txt b/Documentation/rev-list-options.txt
index a9b808f..f1c5220 100644
--- a/Documentation/rev-list-options.txt
+++ b/Documentation/rev-list-options.txt
@@ -58,9 +58,11 @@ endif::git-rev-list[]
 	more than one `--grep=<pattern>`, commits whose message
 	matches any of the given patterns are chosen (but see
 	`--all-match`).
+ifndef::git-rev-list[]
 +
 When `--show-notes` is in effect, the message from the notes is
 matched as if it were part of the log message.
+endif::git-rev-list[]
 
 --all-match::
 	Limit the commits output to ones that match all given `--grep`,
diff --git a/builtin/rev-list.c b/builtin/rev-list.c
index c0b4b53..d80d1ed 100644
--- a/builtin/rev-list.c
+++ b/builtin/rev-list.c
@@ -350,6 +350,9 @@ int cmd_rev_list(int argc, const char **argv, const char *prefix)
 	    revs.diff)
 		usage(rev_list_usage);
 
+	if (revs.show_notes)
+		die(_("rev-list does not support display of notes"));
+
 	save_commit_buffer = (revs.verbose_header ||
 			      revs.grep_filter.pattern_list ||
 			      revs.grep_filter.header_list);