pretty: enable --expand-tabs by default for selected pretty formats

"git log --pretty={medium,full,fuller}" and "git log" by default
prepend 4 spaces to the log message, so it makes sense to enable
the new "expand-tabs" facility by default for these formats.
Add --no-expand-tabs option to override the new default.

The change alone breaks a test in t4201 that runs "git shortlog"
on the output from "git log", and expects that the output from
"git log" does not do such a tab expansion.  Adjust the test to
explicitly disable expand-tabs with --no-expand-tabs.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/pretty-options.txt

@@ -43,9 +43,15 @@ people using 80-column terminals.
 	commit may be copied to the output.
 
 --expand-tabs::
+--no-expand-tabs::
 	Perform a tab expansion (replace each tab with enough spaces
 	to fill to the next display column that is multiple of 8)
 	in the log message before showing it in the output.
++
+By default, tabs are expanded in pretty formats that indent the log
+message by 4 spaces (i.e.  'medium', which is the default, 'full',
+and 'fuller').  `--no-expand-tabs` option can be used to disable
+this.
 
 ifndef::git-rev-list[]
 --notes[=<ref>]::

builtin/log.c

@@ -1281,6 +1281,7 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 	git_config(git_format_config, NULL);
 	init_revisions(&rev, prefix);
 	rev.commit_format = CMIT_FMT_EMAIL;
+	rev.expand_tabs_in_log_default = 0;
 	rev.verbose_header = 1;
 	rev.diff = 1;
 	rev.max_parents = 1;

pretty.c

@@ -16,6 +16,7 @@ static struct cmt_fmt_map {
 	const char *name;
 	enum cmit_fmt format;
 	int is_tformat;
+	int expand_tabs_in_log;
 	int is_alias;
 	const char *user_format;
 } *commit_formats;
@@ -87,13 +88,13 @@ static int git_pretty_formats_config(const char *var, const char *value, void *c
 static void setup_commit_formats(void)
 {
 	struct cmt_fmt_map builtin_formats[] = {
-		{ "raw",	CMIT_FMT_RAW,		0 },
+		{ "raw",	CMIT_FMT_RAW,		0,	0 },
-		{ "medium",	CMIT_FMT_MEDIUM,	0 },
+		{ "medium",	CMIT_FMT_MEDIUM,	0,	1 },
-		{ "short",	CMIT_FMT_SHORT,		0 },
+		{ "short",	CMIT_FMT_SHORT,		0,	0 },
-		{ "email",	CMIT_FMT_EMAIL,		0 },
+		{ "email",	CMIT_FMT_EMAIL,		0,	0 },
-		{ "fuller",	CMIT_FMT_FULLER,	0 },
+		{ "fuller",	CMIT_FMT_FULLER,	0,	1 },
-		{ "full",	CMIT_FMT_FULL,		0 },
+		{ "full",	CMIT_FMT_FULL,		0,	1 },
-		{ "oneline",	CMIT_FMT_ONELINE,	1 }
+		{ "oneline",	CMIT_FMT_ONELINE,	1,	0 }
 	};
 	commit_formats_len = ARRAY_SIZE(builtin_formats);
 	builtin_formats_len = commit_formats_len;
@@ -172,6 +173,7 @@ void get_commit_format(const char *arg, struct rev_info *rev)
 
 	rev->commit_format = commit_format->format;
 	rev->use_terminator = commit_format->is_tformat;
+	rev->expand_tabs_in_log_default = commit_format->expand_tabs_in_log;
 	if (commit_format->format == CMIT_FMT_USERFORMAT) {
 		save_user_format(rev, commit_format->user_format,
 				 commit_format->is_tformat);
@@ -1720,6 +1722,8 @@ void pp_remainder(struct pretty_print_context *pp,
 		strbuf_grow(sb, linelen + indent + 20);
 		if (indent)
 			pp_handle_indent(pp, sb, indent, line, linelen);
+		else if (pp->expand_tabs_in_log)
+			strbuf_add_tabexpand(sb, line, linelen);
 		else
 			strbuf_add(sb, line, linelen);
 		strbuf_addch(sb, '\n');

revision.c

@@ -1412,8 +1412,10 @@ void init_revisions(struct rev_info *revs, const char *prefix)
 	revs->skip_count = -1;
 	revs->max_count = -1;
 	revs->max_parents = -1;
+	revs->expand_tabs_in_log = -1;
 
 	revs->commit_format = CMIT_FMT_DEFAULT;
+	revs->expand_tabs_in_log_default = 1;
 
 	init_grep_defaults();
 	grep_init(&revs->grep_filter, prefix);
@@ -1917,6 +1919,8 @@ static int handle_revision_opt(struct rev_info *revs, int argc, const char **arg
 		get_commit_format(arg+9, revs);
 	} else if (!strcmp(arg, "--expand-tabs")) {
 		revs->expand_tabs_in_log = 1;
+	} else if (!strcmp(arg, "--no-expand-tabs")) {
+		revs->expand_tabs_in_log = 0;
 	} else if (!strcmp(arg, "--show-notes") || !strcmp(arg, "--notes")) {
 		revs->show_notes = 1;
 		revs->show_notes_given = 1;
@@ -2390,6 +2394,9 @@ int setup_revisions(int argc, const char **argv, struct rev_info *revs, struct s
 	if (revs->first_parent_only && revs->bisect)
 		die(_("--first-parent is incompatible with --bisect"));
 
+	if (revs->expand_tabs_in_log < 0)
+		revs->expand_tabs_in_log = revs->expand_tabs_in_log_default;
+
 	return left;
 }
 

revision.h

@@ -133,7 +133,6 @@ struct rev_info {
 			show_notes_given:1,
 			show_signature:1,
 			pretty_given:1,
-			expand_tabs_in_log:1,
 			abbrev_commit:1,
 			abbrev_commit_given:1,
 			zero_commit:1,
@@ -149,6 +148,8 @@ struct rev_info {
 			linear:1;
 
 	struct date_mode date_mode;
+	int		expand_tabs_in_log; /* unset if negative */
+	int		expand_tabs_in_log_default;
 
 	unsigned int	abbrev;
 	enum cmit_fmt	commit_format;

t/t4201-shortlog.sh

@@ -115,7 +115,7 @@ EOF
 '
 
 test_expect_success !MINGW 'shortlog from non-git directory' '
-	git log HEAD >log &&
+	git log --no-expand-tabs HEAD >log &&
 	GIT_DIR=non-existing git shortlog -w <log >out &&
 	test_cmp expect out
 '