[RFC PATCH] log: add log.showStat configuration variable

[Robert Karszniewicz <avoidr@posteo.de>]

Changes default behaviour of `git log` and `git show` when no
command-line options are given. Doesn't affect behaviour otherwise (same
behaviour as with stash.showStat).
---
I've wanted to have `show` and `log` show --stat by default, and I
couldn't find any better solution for it. And I've discovered that there
is stash.showStat, which is exactly what I want. So I wanted to bring
stash.showStat to `show` and `log`.

So far, setting log.showStat affects behaviour as described in the
commit message.
But it does so for `show` and `log` at the same time. I think they
should be configurable separately. (log.showStat and show.showStat)

Before I do all the work, please tell me if this is the right approach
so far, and if the feature - when ready - would be accepted. (I'm aware
that documentation and tests are missing.)

 builtin/log.c | 22 ++++++++++++++++++----
 revision.h    |  1 +
 2 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/builtin/log.c b/builtin/log.c
index 0a7ed4bef9..225252f0b4 100644
--- a/builtin/log.c
+++ b/builtin/log.c
@@ -45,6 +45,7 @@ static int default_abbrev_commit;
 static int default_show_root = 1;
 static int default_follow;
 static int default_show_signature;
+static int default_show_stat;
 static int default_encode_email_headers = 1;
 static int decoration_style;
 static int decoration_given;
@@ -151,6 +152,7 @@ static void cmd_log_init_defaults(struct rev_info *rev)
 	rev->show_root_diff = default_show_root;
 	rev->subject_prefix = fmt_patch_subject_prefix;
 	rev->show_signature = default_show_signature;
+	rev->show_stat = default_show_stat;
 	rev->encode_email_headers = default_encode_email_headers;
 	rev->diffopt.flags.allow_textconv = 1;
 
@@ -488,6 +490,10 @@ static int git_log_config(const char *var, const char *value, void *cb)
 		default_show_signature = git_config_bool(var, value);
 		return 0;
 	}
+	if (!strcmp(var, "log.showstat")) {
+		default_show_stat = git_config_bool(var, value);
+		return 0;
+	}
 
 	if (grep_config(var, value, cb) < 0)
 		return -1;
@@ -607,8 +613,11 @@ static void show_setup_revisions_tweak(struct rev_info *rev,
 			rev->dense_combined_merges = 1;
 		}
 	}
-	if (!rev->diffopt.output_format)
+	if (!rev->diffopt.output_format) {
 		rev->diffopt.output_format = DIFF_FORMAT_PATCH;
+		if (rev->show_stat)
+			rev->diffopt.output_format |= DIFF_FORMAT_DIFFSTAT;
+	}
 }
 
 int cmd_show(int argc, const char **argv, const char *prefix)
@@ -727,9 +736,14 @@ static void log_setup_revisions_tweak(struct rev_info *rev,
 	    rev->prune_data.nr == 1)
 		rev->diffopt.flags.follow_renames = 1;
 
-	/* Turn --cc/-c into -p --cc/-c when -p was not given */
-	if (!rev->diffopt.output_format && rev->combine_merges)
-		rev->diffopt.output_format = DIFF_FORMAT_PATCH;
+	if (!rev->diffopt.output_format) {
+		/* Turn --cc/-c into -p --cc/-c when -p was not given */
+		if (rev->combine_merges)
+			rev->diffopt.output_format = DIFF_FORMAT_PATCH;
+
+		if (rev->show_stat)
+			rev->diffopt.output_format |= DIFF_FORMAT_DIFFSTAT;
+	}
 
 	if (rev->first_parent_only && rev->ignore_merges < 0)
 		rev->ignore_merges = 0;
diff --git a/revision.h b/revision.h
index f6bf860d19..e402c519d8 100644
--- a/revision.h
+++ b/revision.h
@@ -204,6 +204,7 @@ struct rev_info {
 			show_merge:1,
 			show_notes_given:1,
 			show_signature:1,
+			show_stat:1,
 			pretty_given:1,
 			abbrev_commit:1,
 			abbrev_commit_given:1,
-- 
2.28.0