Merge branch 'es/format-patch-interdiff' into es/format-patch-rangediff

* es/format-patch-interdiff:
  format-patch: allow --interdiff to apply to a lone-patch
  log-tree: show_log: make commentary block delimiting reusable
  interdiff: teach show_interdiff() to indent interdiff
  format-patch: teach --interdiff to respect -v/--reroll-count
  format-patch: add --interdiff option to embed diff in cover letter
  format-patch: allow additional generated content in make_cover_letter()

8 files changed, 177 insertions, 28 deletions

diff --git a/Documentation/git-format-patch.txt b/Documentation/git-format-patch.txt
index b41e132..f8a0617 100644
--- a/Documentation/git-format-patch.txt
+++ b/Documentation/git-format-patch.txt
@@ -23,6 +23,7 @@ SYNOPSIS
 		   [(--reroll-count|-v) <n>]
 		   [--to=<email>] [--cc=<email>]
 		   [--[no-]cover-letter] [--quiet] [--notes[=<ref>]]
+		   [--interdiff=<previous>]
 		   [--progress]
 		   [<common diff options>]
 		   [ <since> | <revision range> ]
@@ -228,6 +229,15 @@ feeding the result to `git send-email`.
 	containing the branch description, shortlog and the overall diffstat.  You can
 	fill in a description in the file before sending it out.
 
+--interdiff=<previous>::
+	As a reviewer aid, insert an interdiff into the cover letter,
+	or as commentary of the lone patch of a 1-patch series, showing
+	the differences between the previous version of the patch series and
+	the series currently being formatted. `previous` is a single revision
+	naming the tip of the previous series which shares a common base with
+	the series being formatted (for example `git format-patch
+	--cover-letter --interdiff=feature/v1 -3 feature/v2`).
+
 --notes[=<ref>]::
 	Append the notes (see linkgit:git-notes[1]) for the commit
 	after the three-dash line.
diff --git a/Makefile b/Makefile
index 72f1688..12e3c2d 100644
--- a/Makefile
+++ b/Makefile
@@ -874,6 +874,7 @@ LIB_OBJS += linear-assignment.o
 LIB_OBJS += help.o
 LIB_OBJS += hex.o
 LIB_OBJS += ident.o
+LIB_OBJS += interdiff.o
 LIB_OBJS += kwset.o
 LIB_OBJS += levenshtein.o
 LIB_OBJS += line-log.o
diff --git a/builtin/log.c b/builtin/log.c
index 5745951..fcc2f4d 100644
--- a/builtin/log.c
+++ b/builtin/log.c
@@ -31,6 +31,7 @@
 #include "progress.h"
 #include "commit-slab.h"
 #include "repository.h"
+#include "interdiff.h"
 
 #define MAIL_DEFAULT_WRAP 72
 
@@ -998,6 +999,26 @@ static char *find_branch_name(struct rev_info *rev)
 	return branch;
 }
 
+static void show_diffstat(struct rev_info *rev,
+			  struct commit *origin, struct commit *head)
+{
+	struct diff_options opts;
+
+	memcpy(&opts, &rev->diffopt, sizeof(opts));
+	opts.output_format = DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
+	opts.stat_width = MAIL_DEFAULT_WRAP;
+
+	diff_setup_done(&opts);
+
+	diff_tree_oid(get_commit_tree_oid(origin),
+		      get_commit_tree_oid(head),
+		      "", &opts);
+	diffcore_std(&opts);
+	diff_flush(&opts);
+
+	fprintf(rev->diffopt.file, "\n");
+}
+
 static void make_cover_letter(struct rev_info *rev, int use_stdout,
 			      struct commit *origin,
 			      int nr, struct commit **list,
@@ -1011,7 +1032,6 @@ static void make_cover_letter(struct rev_info *rev, int use_stdout,
 	struct strbuf sb = STRBUF_INIT;
 	int i;
 	const char *encoding = "UTF-8";
-	struct diff_options opts;
 	int need_8bit_cte = 0;
 	struct pretty_print_context pp = {0};
 	struct commit *head = list[0];
@@ -1061,25 +1081,14 @@ static void make_cover_letter(struct rev_info *rev, int use_stdout,
 
 	shortlog_output(&log);
 
-	/*
-	 * We can only do diffstat with a unique reference point
-	 */
-	if (!origin)
-		return;
+	/* We can only do diffstat with a unique reference point */
+	if (origin)
+		show_diffstat(rev, origin, head);
 
-	memcpy(&opts, &rev->diffopt, sizeof(opts));
-	opts.output_format = DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
-	opts.stat_width = MAIL_DEFAULT_WRAP;
-
-	diff_setup_done(&opts);
-
-	diff_tree_oid(get_commit_tree_oid(origin),
-		      get_commit_tree_oid(head),
-		      "", &opts);
-	diffcore_std(&opts);
-	diff_flush(&opts);
-
-	fprintf(rev->diffopt.file, "\n");
+	if (rev->idiff_oid1) {
+		fprintf_ln(rev->diffopt.file, "%s", rev->idiff_title);
+		show_interdiff(rev, 0);
+	}
 }
 
 static const char *clean_message_id(const char *msg_id)
@@ -1419,6 +1428,16 @@ static void print_bases(struct base_tree_info *bases, FILE *file)
 	oidclr(&bases->base_commit);
 }
 
+static const char *diff_title(struct strbuf *sb, int reroll_count,
+		       const char *generic, const char *rerolled)
+{
+	if (reroll_count <= 0)
+		strbuf_addstr(sb, generic);
+	else /* RFC may be v0, so allow -v1 to diff against v0 */
+		strbuf_addf(sb, rerolled, reroll_count - 1);
+	return sb->buf;
+}
+
 int cmd_format_patch(int argc, const char **argv, const char *prefix)
 {
 	struct commit *commit;
@@ -1446,6 +1465,8 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 	struct base_tree_info bases;
 	int show_progress = 0;
 	struct progress *progress = NULL;
+	struct oid_array idiff_prev = OID_ARRAY_INIT;
+	struct strbuf idiff_title = STRBUF_INIT;
 
 	const struct option builtin_format_patch_options[] = {
 		{ OPTION_CALLBACK, 'n', "numbered", &numbered, NULL,
@@ -1519,6 +1540,9 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 		OPT__QUIET(&quiet, N_("don't print the patch filenames")),
 		OPT_BOOL(0, "progress", &show_progress,
 			 N_("show progress while generating patches")),
+		OPT_CALLBACK(0, "interdiff", &idiff_prev, N_("rev"),
+			     N_("show changes against <rev> in cover letter or single patch"),
+			     parse_opt_object_name),
 		OPT_END()
 	};
 
@@ -1704,7 +1728,7 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 		if (rev.pending.nr == 2) {
 			struct object_array_entry *o = rev.pending.objects;
 			if (oidcmp(&o[0].item->oid, &o[1].item->oid) == 0)
-				return 0;
+				goto done;
 		}
 		get_patch_ids(&rev, &ids);
 	}
@@ -1728,7 +1752,7 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 	}
 	if (nr == 0)
 		/* nothing to do */
-		return 0;
+		goto done;
 	total = nr;
 	if (cover_letter == -1) {
 		if (config_cover_letter == COVER_AUTO)
@@ -1741,6 +1765,16 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 	if (numbered)
 		rev.total = total + start_number - 1;
 
+	if (idiff_prev.nr) {
+		if (!cover_letter && total != 1)
+			die(_("--interdiff requires --cover-letter or single patch"));
+		rev.idiff_oid1 = &idiff_prev.oid[idiff_prev.nr - 1];
+		rev.idiff_oid2 = get_commit_tree_oid(list[0]);
+		rev.idiff_title = diff_title(&idiff_title, reroll_count,
+					     _("Interdiff:"),
+					     _("Interdiff against v%d:"));
+	}
+
 	if (!signature) {
 		; /* --no-signature inhibits all signatures */
 	} else if (signature && signature != git_version_string) {
@@ -1778,6 +1812,8 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 		print_signature(rev.diffopt.file);
 		total++;
 		start_number--;
+		/* interdiff in cover-letter; omit from patches */
+		rev.idiff_oid1 = NULL;
 	}
 	rev.add_signoff = do_signoff;
 
@@ -1858,6 +1894,10 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 	string_list_clear(&extra_hdr, 0);
 	if (ignore_if_in_upstream)
 		free_patch_ids(&ids);
+
+done:
+	oid_array_clear(&idiff_prev);
+	strbuf_release(&idiff_title);
 	return 0;
 }
 
diff --git a/interdiff.c b/interdiff.c
new file mode 100644
index 0000000..c81d680
--- /dev/null
+++ b/interdiff.c
@@ -0,0 +1,28 @@
+#include "cache.h"
+#include "commit.h"
+#include "revision.h"
+#include "interdiff.h"
+
+static struct strbuf *idiff_prefix_cb(struct diff_options *opt, void *data)
+{
+	return data;
+}
+
+void show_interdiff(struct rev_info *rev, int indent)
+{
+	struct diff_options opts;
+	struct strbuf prefix = STRBUF_INIT;
+
+	memcpy(&opts, &rev->diffopt, sizeof(opts));
+	opts.output_format = DIFF_FORMAT_PATCH;
+	opts.output_prefix = idiff_prefix_cb;
+	strbuf_addchars(&prefix, ' ', indent);
+	opts.output_prefix_data = &prefix;
+	diff_setup_done(&opts);
+
+	diff_tree_oid(rev->idiff_oid1, rev->idiff_oid2, "", &opts);
+	diffcore_std(&opts);
+	diff_flush(&opts);
+
+	strbuf_release(&prefix);
+}
diff --git a/interdiff.h b/interdiff.h
new file mode 100644
index 0000000..01c730a
--- /dev/null
+++ b/interdiff.h
@@ -0,0 +1,8 @@
+#ifndef INTERDIFF_H
+#define INTERDIFF_H
+
+struct rev_info;
+
+void show_interdiff(struct rev_info *, int indent);
+
+#endif
diff --git a/log-tree.c b/log-tree.c
index c0ac7af..e21c3d9 100644
--- a/log-tree.c
+++ b/log-tree.c
@@ -15,6 +15,7 @@
 #include "sequencer.h"
 #include "line-log.h"
 #include "help.h"
+#include "interdiff.h"
 
 static struct decoration name_decoration = { "object names" };
 static int decoration_loaded;
@@ -542,6 +543,16 @@ static int show_mergetag(struct rev_info *opt, struct commit *commit)
 	return for_each_mergetag(show_one_mergetag, commit, opt);
 }
 
+static void next_commentary_block(struct rev_info *opt, struct strbuf *sb)
+{
+	const char *x = opt->shown_dashes ? "\n" : "---\n";
+	if (sb)
+		strbuf_addstr(sb, x);
+	else
+		fputs(x, opt->diffopt.file);
+	opt->shown_dashes = 1;
+}
+
 void show_log(struct rev_info *opt)
 {
 	struct strbuf msgbuf = STRBUF_INIT;
@@ -699,10 +710,8 @@ void show_log(struct rev_info *opt)
 
 	if ((ctx.fmt != CMIT_FMT_USERFORMAT) &&
 	    ctx.notes_message && *ctx.notes_message) {
-		if (cmit_fmt_is_mail(ctx.fmt)) {
-			strbuf_addstr(&msgbuf, "---\n");
-			opt->shown_dashes = 1;
-		}
+		if (cmit_fmt_is_mail(ctx.fmt))
+			next_commentary_block(opt, &msgbuf);
 		strbuf_addstr(&msgbuf, ctx.notes_message);
 	}
 
@@ -729,6 +738,19 @@ void show_log(struct rev_info *opt)
 
 	strbuf_release(&msgbuf);
 	free(ctx.notes_message);
+
+	if (cmit_fmt_is_mail(ctx.fmt) && opt->idiff_oid1) {
+		struct diff_queue_struct dq;
+
+		memcpy(&dq, &diff_queued_diff, sizeof(diff_queued_diff));
+		DIFF_QUEUE_CLEAR(&diff_queued_diff);
+
+		next_commentary_block(opt, NULL);
+		fprintf_ln(opt->diffopt.file, "%s", opt->idiff_title);
+		show_interdiff(opt, 2);
+
+		memcpy(&diff_queued_diff, &dq, sizeof(diff_queued_diff));
+	}
 }
 
 int log_tree_diff_flush(struct rev_info *opt)
@@ -766,9 +788,10 @@ int log_tree_diff_flush(struct rev_info *opt)
 
 			/*
 			 * We may have shown three-dashes line early
-			 * between notes and the log message, in which
-			 * case we only want a blank line after the
-			 * notes without (an extra) three-dashes line.
+			 * between generated commentary (notes, etc.)
+			 * and the log message, in which case we only
+			 * want a blank line after the commentary
+			 * without (an extra) three-dashes line.
 			 * Otherwise, we show the three-dashes line if
 			 * we are showing the patch with diffstat, but
 			 * in that case, there is no extra blank line
diff --git a/revision.h b/revision.h
index c599c34..b30ea3a 100644
--- a/revision.h
+++ b/revision.h
@@ -213,6 +213,11 @@ struct rev_info {
 	/* notes-specific options: which refs to show */
 	struct display_notes_opt notes_opt;
 
+	/* interdiff */
+	const struct object_id *idiff_oid1;
+	const struct object_id *idiff_oid2;
+	const char *idiff_title;
+
 	/* commit counts */
 	int count_left;
 	int count_right;
diff --git a/t/t4014-format-patch.sh b/t/t4014-format-patch.sh
index 53880da..909c743 100755
--- a/t/t4014-format-patch.sh
+++ b/t/t4014-format-patch.sh
@@ -1717,4 +1717,38 @@ test_expect_success 'format-patch --pretty=mboxrd' '
 	test_cmp expect actual
 '
 
+test_expect_success 'interdiff: setup' '
+	git checkout -b boop master &&
+	test_commit fnorp blorp &&
+	test_commit fleep blorp
+'
+
+test_expect_success 'interdiff: cover-letter' '
+	sed "y/q/ /" >expect <<-\EOF &&
+	+fleep
+	--q
+	EOF
+	git format-patch --cover-letter --interdiff=boop~2 -1 boop &&
+	test_i18ngrep "^Interdiff:$" 0000-cover-letter.patch &&
+	test_i18ngrep ! "^Interdiff:$" 0001-fleep.patch &&
+	sed "1,/^@@ /d; /^-- $/q" <0000-cover-letter.patch >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'interdiff: reroll-count' '
+	git format-patch --cover-letter --interdiff=boop~2 -v2 -1 boop &&
+	test_i18ngrep "^Interdiff ..* v1:$" v2-0000-cover-letter.patch
+'
+
+test_expect_success 'interdiff: solo-patch' '
+	cat >expect <<-\EOF &&
+	  +fleep
+
+	EOF
+	git format-patch --interdiff=boop~2 -1 boop &&
+	test_i18ngrep "^Interdiff:$" 0001-fleep.patch &&
+	sed "1,/^  @@ /d; /^$/q" <0001-fleep.patch >actual &&
+	test_cmp expect actual
+'
+
 test_done