log/show/whatchanged: introduce format.pretty configuration

When running log/show/whatchanged from the command line, the user may
want to use a preferred format without having to pass --pretty=<fmt>
option every time from the command line.  This teaches these three
commands to honor a new configuration variable, format.pretty.

The --pretty option given from the command line will override the
configured format.

The earlier patch fixed the in-tree callers that run these commands
for purposes other than showing the output directly to the end user
(the only other in-tree caller is "git bisect visualize", whose output
directly goes to the end user and should be affected by this patch).

Similar fixes will be needed for end-user scripts that parse the
output from these commands and expect them to be in the default pretty
format.

Signed-off-by: Denis Cheng <crquan@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config.txt

@@ -556,6 +556,11 @@ format.suffix::
 	`.patch`. Use this variable to change that suffix (make sure to
 	include the dot if you want it).
 
+format.pretty::
+	The default pretty format for log/show/whatchanged command,
+	See linkgit:git-log[1], linkgit:git-show[1],
+	linkgit:git-whatchanged[1].
+
 gc.aggressiveWindow::
 	The window size parameter used in the delta compression
 	algorithm used by 'git gc --aggressive'.  This defaults

Documentation/pretty-options.txt

@@ -4,6 +4,9 @@
 	where '<format>' can be one of 'oneline', 'short', 'medium',
 	'full', 'fuller', 'email', 'raw' and 'format:<string>'.
 	When omitted, the format defaults to 'medium'.
++
+Note: you can specify the default pretty format in the repository
+configuration (see linkgit:git-config[1]).
 
 --abbrev-commit::
 	Instead of showing the full 40-byte hexadecimal commit object

builtin-log.c

@@ -20,6 +20,7 @@
 
 static int default_show_root = 1;
 static const char *fmt_patch_subject_prefix = "PATCH";
+static const char *fmt_pretty;
 
 static void add_name_decoration(const char *prefix, const char *name, struct object *obj)
 {
@@ -54,6 +55,8 @@ static void cmd_log_init(int argc, const char **argv, const char *prefix,
 
 	rev->abbrev = DEFAULT_ABBREV;
 	rev->commit_format = CMIT_FMT_DEFAULT;
+	if (fmt_pretty)
+		rev->commit_format = get_commit_format(fmt_pretty);
 	rev->verbose_header = 1;
 	DIFF_OPT_SET(&rev->diffopt, RECURSIVE);
 	rev->show_root_diff = default_show_root;
@@ -221,6 +224,8 @@ static int cmd_log_walk(struct rev_info *rev)
 
 static int git_log_config(const char *var, const char *value)
 {
+	if (!strcmp(var, "format.pretty"))
+		return git_config_string(&fmt_pretty, var, value);
 	if (!strcmp(var, "format.subjectprefix")) {
 		if (!value)
 			config_error_nonbool(var);