Re: [PATCH] Initialize notes trees if %N is used and no --show-notes given

[Jeff King <peff@peff.net>]

On Tue, Apr 06, 2010 at 11:18:34PM -0700, Junio C Hamano wrote:

> As Peff pointed out, %d does things lazily, but I suspect it might be hard
> to do a similar initialization for %N.

I think you would just have to stuff the notes-related options from the
rev-list options into the pretty-print context, which would then make
them available to the user-format callback.

> I wonder if we can inspect-but-not-use format string before we even start
> walking, to see if we need notes (when we see %N).

I have considered something like the patch below before, but it is not
100% accurate. Part of the parsing happens in strbuf_expand, but parsing
of things like %w(...) happens ad-hoc inside the formatting callback (so
we would see "%w(%N)" as wanting notes, when it doesn't really. In
theory it would be nicer if we separated syntax and semantics, so I
could parse %X(...) as "the %X placeholder with ... as arguments"
without having to actually understand what %X does. In practice, it
doesn't matter here because we don't have very many placeholders that
take arbitrary arguments.

The patch below is totally untested and just meant to illustrate the
approach. Use caution.

diff --git a/commit.h b/commit.h
index 2b7fd89..5081389 100644
--- a/commit.h
+++ b/commit.h
@@ -74,11 +74,16 @@ struct pretty_print_context
 	struct reflog_walk_info *reflog_info;
 };
 
+struct userformat_want {
+	unsigned notes:1;
+};
+
 extern int has_non_ascii(const char *text);
 struct rev_info; /* in revision.h, it circularly uses enum cmit_fmt */
 extern char *reencode_commit_message(const struct commit *commit,
 				     const char **encoding_p);
 extern void get_commit_format(const char *arg, struct rev_info *);
+extern void userformat_fill_want(const char *format, struct userformat_want *w);
 extern void format_commit_message(const struct commit *commit,
 				  const char *format, struct strbuf *sb,
 				  const struct pretty_print_context *context);
diff --git a/pretty.c b/pretty.c
index 6ba3da8..8ed3d36 100644
--- a/pretty.c
+++ b/pretty.c
@@ -855,6 +855,24 @@ static size_t format_commit_item(struct strbuf *sb, const char *placeholder,
 	return consumed + 1;
 }
 
+static size_t userformat_want_item(struct strbuf *sb, const char *placeholder,
+				 void *context)
+{
+	struct userformat_want *w = context;
+	switch (*placeholder) {
+		case 'N': w->notes = 1;
+	}
+	return 0;
+}
+
+void userformat_fill_want(const char *format, struct userformat_want *w)
+{
+	struct strbuf dummy = STRBUF_INIT;
+	memset(w, 0, sizeof(*w));
+	strbuf_expand(&dummy, format, userformat_want_item, w);
+	strbuf_release(&dummy);
+}
+
 void format_commit_message(const struct commit *commit,
 			   const char *format, struct strbuf *sb,
 			   const struct pretty_print_context *pretty_ctx)