pretty: drop print_email_subject flag

With one exception, the print_email_subject flag is set if and only if
the commit format is email based:

  - in make_cover_letter() we set it along with CMIT_FMT_EMAIL
    explicitly

  - in show_log(), we set it if cmit_fmt_is_mail() is true. That covers
    format-patch as well as "git log --format=email" (or mboxrd).

The one exception is "rev-list --format=email", which somewhat
nonsensically prints the author and date as email headers, but no
subject, like:

  $ git rev-list --format=email HEAD
  commit 64fc4c2cdd4db2645eaabb47aa4bac820b03cdba
  From: Jeff King <peff@peff.net>
  Date: Tue, 19 Mar 2024 19:39:26 -0400

  this is the subject

  this is the body

It's doubtful that this is a useful format at all (the "commit" lines
replace the "From" lines that would make it work as an actual mbox).
But I think that printing the subject as a header (like this patch does)
is the least surprising thing to do.

So let's drop this field, making the code a little simpler and easier to
reason about. Note that we do need to set the "rev" field of the
pretty_print_context in rev-list, since that is used to check for
subject_prefix, etc. It's not possible to set those fields via rev-list,
so we'll always just print "Subject: ". But unless we pass in our
rev_info, fmt_output_email_subject() would segfault trying to figure it
out.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 8 insertions, 13 deletions

diff --git a/pretty.c b/pretty.c
index 397d282..3df00bc 100644
--- a/pretty.c
+++ b/pretty.c
@@ -2091,19 +2091,14 @@ void pp_email_subject(struct pretty_print_context *pp,
 				pp->preserve_subject ? "\n" : " ");
 
 	strbuf_grow(sb, title.len + 1024);
-	if (pp->print_email_subject) {
-		if (pp->rev)
-			fmt_output_email_subject(sb, pp->rev);
-		if (pp->encode_email_headers &&
-		    needs_rfc2047_encoding(title.buf, title.len))
-			add_rfc2047(sb, title.buf, title.len,
-						encoding, RFC2047_SUBJECT);
-		else
-			strbuf_add_wrapped_bytes(sb, title.buf, title.len,
+	fmt_output_email_subject(sb, pp->rev);
+	if (pp->encode_email_headers &&
+	    needs_rfc2047_encoding(title.buf, title.len))
+		add_rfc2047(sb, title.buf, title.len,
+			    encoding, RFC2047_SUBJECT);
+	else
+		strbuf_add_wrapped_bytes(sb, title.buf, title.len,
 					 -last_line_length(sb), 1, max_length);
-	} else {
-		strbuf_addbuf(sb, &title);
-	}
 	strbuf_addch(sb, '\n');
 
 	if (need_8bit_cte == 0) {
@@ -2319,7 +2314,7 @@ void pretty_print_commit(struct pretty_print_context *pp,
 	}
 
 	pp_header(pp, encoding, commit, &msg, sb);
-	if (pp->fmt != CMIT_FMT_ONELINE && !pp->print_email_subject) {
+	if (pp->fmt != CMIT_FMT_ONELINE && !cmit_fmt_is_mail(pp->fmt)) {
 		strbuf_addch(sb, '\n');
 	}