[PATCH v4 1/2] diff: add --line-prefix option for passing in a prefix

[PATCH v4 1/2] diff: add --line-prefix option for passing in a prefix

[Jacob Keller]

From: Jacob Keller <jacob.keller@gmail.com>

This will be used by a future patch which implements a diff mode for
submodule display. Without this, the diff output would incorrectly
display when using both -p and --graph during a git-log.

Note that the --line-prefix will be displayed first prior to any other
output prefix.

Signed-off-by: Jacob Keller <jacob.keller@gmail.com>
---
 Documentation/diff-options.txt |  3 +++
 diff.c                         | 13 ++++++++++++-
 diff.h                         |  1 +
 3 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/Documentation/diff-options.txt b/Documentation/diff-options.txt
index 705a87394200..e7b729f3644f 100644
--- a/Documentation/diff-options.txt
+++ b/Documentation/diff-options.txt
@@ -569,5 +569,8 @@ endif::git-format-patch[]
 --no-prefix::
 	Do not show any source or destination prefix.
 
+--line-prefix=<prefix>::
+	Prepend an additional prefix to every diff output line.
+
 For more detailed explanation on these common options, see also
 linkgit:gitdiffcore[7].
diff --git a/diff.c b/diff.c
index b43d3dd2ecb7..6fa9668b19e5 100644
--- a/diff.c
+++ b/diff.c
@@ -1167,10 +1167,17 @@ const char *diff_get_color(int diff_use_color, enum color_diff ix)
 const char *diff_line_prefix(struct diff_options *opt)
 {
 	struct strbuf *msgbuf;
+
 	if (!opt->output_prefix)
-		return "";
+		if (opt->line_prefix)
+			return opt->line_prefix;
+		else
+			return "";
 
 	msgbuf = opt->output_prefix(opt, opt->output_prefix_data);
+	/* line prefix must be printed before the output_prefix() */
+	if (opt->line_prefix)
+		strbuf_insert(msgbuf, 0, opt->line_prefix, strlen(opt->line_prefix));
 	return msgbuf->buf;
 }
 
@@ -3966,6 +3973,10 @@ int diff_opt_parse(struct diff_options *options,
 		options->a_prefix = optarg;
 		return argcount;
 	}
+	else if ((argcount = parse_long_opt("line-prefix", av, &optarg))) {
+		options->line_prefix = optarg;
+		return argcount;
+	}
 	else if ((argcount = parse_long_opt("dst-prefix", av, &optarg))) {
 		options->b_prefix = optarg;
 		return argcount;
diff --git a/diff.h b/diff.h
index 125447be09eb..6a91a1139686 100644
--- a/diff.h
+++ b/diff.h
@@ -115,6 +115,7 @@ struct diff_options {
 	const char *pickaxe;
 	const char *single_follow;
 	const char *a_prefix, *b_prefix;
+	const char *line_prefix;
 	unsigned flags;
 	unsigned touched_flags;
 
-- 
2.9.2.872.g2dc3c84

[PATCH v4 2/2] diff: add SUBMODULE_DIFF format to display submodule diff

[Jacob Keller]

From: Jacob Keller <jacob.keller@gmail.com>

Teach git-diff and friends a new format for displaying the difference of
a submodule using git-diff inside the submodule project. This allows
users to easily see exactly what source changed in a given commit that
updates the submodule pointer. To do this, remove DIFF_SUBMODULE_LOG bit
from the diff options, and instead add a new enum type for these
formats.

Signed-off-by: Jacob Keller <jacob.keller@gmail.com>
---
 Documentation/diff-config.txt  |  3 +-
 Documentation/diff-options.txt |  6 ++--
 diff.c                         | 41 ++++++++++++++++----------
 diff.h                         |  9 +++++-
 submodule.c                    | 67 ++++++++++++++++++++++++++++++++++++++++++
 submodule.h                    |  6 ++++
 6 files changed, 113 insertions(+), 19 deletions(-)

diff --git a/Documentation/diff-config.txt b/Documentation/diff-config.txt
index d5a5b17d5088..f5d693afad6c 100644
--- a/Documentation/diff-config.txt
+++ b/Documentation/diff-config.txt
@@ -123,7 +123,8 @@ diff.suppressBlankEmpty::
 diff.submodule::
 	Specify the format in which differences in submodules are
 	shown.  The "log" format lists the commits in the range like
-	linkgit:git-submodule[1] `summary` does.  The "short" format
+	linkgit:git-submodule[1] `summary` does.  The "diff" format shows the
+	diff between the beginning and end of the range. The "short" format
 	format just shows the names of the commits at the beginning
 	and end of the range.  Defaults to short.
 
diff --git a/Documentation/diff-options.txt b/Documentation/diff-options.txt
index e7b729f3644f..988068225463 100644
--- a/Documentation/diff-options.txt
+++ b/Documentation/diff-options.txt
@@ -215,8 +215,10 @@ any of those replacements occurred.
 	the commits in the range like linkgit:git-submodule[1] `summary` does.
 	Omitting the `--submodule` option or specifying `--submodule=short`,
 	uses the 'short' format. This format just shows the names of the commits
-	at the beginning and end of the range.  Can be tweaked via the
-	`diff.submodule` configuration variable.
+	at the beginning and end of the range. When `--submodule=diff` is
+	given, the 'diff' format is used. This format shows the diff between
+	the old and new submodule commmit from the perspective of the
+	submodule.  Can be tweaked via the `diff.submodule` configuration variable.
 
 --color[=<when>]::
 	Show colored diff.
diff --git a/diff.c b/diff.c
index 6fa9668b19e5..8a591d23eb0f 100644
--- a/diff.c
+++ b/diff.c
@@ -131,9 +131,11 @@ static int parse_dirstat_params(struct diff_options *options, const char *params
 static int parse_submodule_params(struct diff_options *options, const char *value)
 {
 	if (!strcmp(value, "log"))
-		DIFF_OPT_SET(options, SUBMODULE_LOG);
+		options->submodule_format = DIFF_SUBMODULE_LOG;
+	else if (!strcmp(value, "diff"))
+		options->submodule_format = DIFF_SUBMODULE_DIFF;
 	else if (!strcmp(value, "short"))
-		DIFF_OPT_CLR(options, SUBMODULE_LOG);
+		options->submodule_format = DIFF_SUBMODULE_SHORT;
 	else
 		return -1;
 	return 0;
@@ -2306,9 +2308,18 @@ static void builtin_diff(const char *name_a,
 	struct strbuf header = STRBUF_INIT;
 	const char *line_prefix = diff_line_prefix(o);
 
-	if (DIFF_OPT_TST(o, SUBMODULE_LOG) &&
-			(!one->mode || S_ISGITLINK(one->mode)) &&
-			(!two->mode || S_ISGITLINK(two->mode))) {
+	diff_set_mnemonic_prefix(o, "a/", "b/");
+	if (DIFF_OPT_TST(o, REVERSE_DIFF)) {
+		a_prefix = o->b_prefix;
+		b_prefix = o->a_prefix;
+	} else {
+		a_prefix = o->a_prefix;
+		b_prefix = o->b_prefix;
+	}
+
+	if (o->submodule_format == DIFF_SUBMODULE_LOG &&
+	    (!one->mode || S_ISGITLINK(one->mode)) &&
+	    (!two->mode || S_ISGITLINK(two->mode))) {
 		const char *del = diff_get_color_opt(o, DIFF_FILE_OLD);
 		const char *add = diff_get_color_opt(o, DIFF_FILE_NEW);
 		show_submodule_summary(o->file, one->path ? one->path : two->path,
@@ -2317,6 +2328,15 @@ static void builtin_diff(const char *name_a,
 				two->dirty_submodule,
 				meta, del, add, reset);
 		return;
+	} else if (o->submodule_format == DIFF_SUBMODULE_DIFF &&
+		   (!one->mode || S_ISGITLINK(one->mode)) &&
+		   (!two->mode || S_ISGITLINK(two->mode))) {
+		show_submodule_diff(o->file, one->path ? one->path : two->path,
+				line_prefix,
+				one->oid.hash, two->oid.hash,
+				two->dirty_submodule,
+				meta, a_prefix, b_prefix, reset);
+		return;
 	}
 
 	if (DIFF_OPT_TST(o, ALLOW_TEXTCONV)) {
@@ -2324,15 +2344,6 @@ static void builtin_diff(const char *name_a,
 		textconv_two = get_textconv(two);
 	}
 
-	diff_set_mnemonic_prefix(o, "a/", "b/");
-	if (DIFF_OPT_TST(o, REVERSE_DIFF)) {
-		a_prefix = o->b_prefix;
-		b_prefix = o->a_prefix;
-	} else {
-		a_prefix = o->a_prefix;
-		b_prefix = o->b_prefix;
-	}
-
 	/* Never use a non-valid filename anywhere if at all possible */
 	name_a = DIFF_FILE_VALID(one) ? name_a : name_b;
 	name_b = DIFF_FILE_VALID(two) ? name_b : name_a;
@@ -3922,7 +3933,7 @@ int diff_opt_parse(struct diff_options *options,
 		DIFF_OPT_SET(options, OVERRIDE_SUBMODULE_CONFIG);
 		handle_ignore_submodules_arg(options, arg);
 	} else if (!strcmp(arg, "--submodule"))
-		DIFF_OPT_SET(options, SUBMODULE_LOG);
+		options->submodule_format = DIFF_SUBMODULE_LOG;
 	else if (skip_prefix(arg, "--submodule=", &arg))
 		return parse_submodule_opt(options, arg);
 	else if (skip_prefix(arg, "--ws-error-highlight=", &arg))
diff --git a/diff.h b/diff.h
index 6a91a1139686..3110a2afb3d6 100644
--- a/diff.h
+++ b/diff.h
@@ -83,7 +83,7 @@ typedef struct strbuf *(*diff_prefix_fn_t)(struct diff_options *opt, void *data)
 #define DIFF_OPT_DIRSTAT_BY_FILE     (1 << 20)
 #define DIFF_OPT_ALLOW_TEXTCONV      (1 << 21)
 #define DIFF_OPT_DIFF_FROM_CONTENTS  (1 << 22)
-#define DIFF_OPT_SUBMODULE_LOG       (1 << 23)
+/* (1 << 23) unused */
 #define DIFF_OPT_DIRTY_SUBMODULES    (1 << 24)
 #define DIFF_OPT_IGNORE_UNTRACKED_IN_SUBMODULES (1 << 25)
 #define DIFF_OPT_IGNORE_DIRTY_SUBMODULES (1 << 26)
@@ -110,6 +110,12 @@ enum diff_words_type {
 	DIFF_WORDS_COLOR
 };
 
+enum diff_submodule_format {
+	DIFF_SUBMODULE_SHORT = 0,
+	DIFF_SUBMODULE_LOG,
+	DIFF_SUBMODULE_DIFF
+};
+
 struct diff_options {
 	const char *orderfile;
 	const char *pickaxe;
@@ -156,6 +162,7 @@ struct diff_options {
 	int stat_count;
 	const char *word_regex;
 	enum diff_words_type word_diff;
+	enum diff_submodule_format submodule_format;
 
 	/* this is set by diffcore for DIFF_FORMAT_PATCH */
 	int found_changes;
diff --git a/submodule.c b/submodule.c
index 1b5cdfb7e784..36f8fd00c3ce 100644
--- a/submodule.c
+++ b/submodule.c
@@ -333,6 +333,73 @@ static void print_submodule_summary(struct rev_info *rev, FILE *f,
 	strbuf_release(&sb);
 }
 
+void show_submodule_diff(FILE *f, const char *path,
+		const char *line_prefix,
+		unsigned char one[20], unsigned char two[20],
+		unsigned dirty_submodule, const char *meta,
+		const char *a_prefix, const char *b_prefix,
+		const char *reset)
+{
+	struct child_process cp = CHILD_PROCESS_INIT;
+	struct strbuf sb = STRBUF_INIT;
+	struct strbuf submodule_git_dir = STRBUF_INIT;
+	const char *git_dir, *message = NULL;
+	int create_dirty_diff = 0;
+	FILE *diff;
+	char c;
+
+	if ((dirty_submodule & DIRTY_SUBMODULE_UNTRACKED) ||
+	    (dirty_submodule & DIRTY_SUBMODULE_MODIFIED))
+		create_dirty_diff = 1;
+
+	strbuf_addf(&sb, "%s%sSubmodule %s %s..", line_prefix, meta, path,
+			find_unique_abbrev(one, DEFAULT_ABBREV));
+	strbuf_addf(&sb, "%s:%s\n", !create_dirty_diff ?
+		    find_unique_abbrev(two, DEFAULT_ABBREV) : "", reset);
+	fwrite(sb.buf, sb.len, 1, f);
+
+	strbuf_addf(&submodule_git_dir, "%s/.git", path);
+	git_dir = read_gitfile(submodule_git_dir.buf);
+	if (!git_dir)
+		git_dir = submodule_git_dir.buf;
+	if (!is_directory(git_dir)) {
+		strbuf_reset(&submodule_git_dir);
+		strbuf_addf(&submodule_git_dir, ".git/modules/%s", path);
+		git_dir = submodule_git_dir.buf;
+	}
+
+	fflush(f);
+
+	cp.git_cmd = 1;
+	if (!create_dirty_diff)
+		cp.dir = git_dir;
+	else
+		cp.dir = path;
+	cp.out = dup(fileno(f));
+	cp.no_stdin = 1;
+	argv_array_push(&cp.args, "diff");
+	argv_array_pushf(&cp.args, "--line-prefix=%s", line_prefix);
+	argv_array_pushf(&cp.args, "--src-prefix=%s%s/", a_prefix, path);
+	argv_array_pushf(&cp.args, "--dst-prefix=%s%s/", b_prefix, path);
+	argv_array_push(&cp.args, sha1_to_hex(one));
+
+	/*
+	 * If the submodule has untracked or modified contents don't add the
+	 * current stored commit. Thus, we will diff between the previous
+	 * value and the current tip of working tree. The result is a complete
+	 * diff which shows all changes to the submodule, not just changes
+	 * that have been committed to the super project.
+	 */
+	if (!create_dirty_diff)
+		argv_array_push(&cp.args, sha1_to_hex(two));
+
+	if (run_command(&cp))
+		fprintf(f, "(diff failed)\n");
+
+	strbuf_release(&submodule_git_dir);
+	strbuf_release(&sb);
+}
+
 void show_submodule_summary(FILE *f, const char *path,
 		const char *line_prefix,
 		unsigned char one[20], unsigned char two[20],
diff --git a/submodule.h b/submodule.h
index 2af939099819..f32a25c667ab 100644
--- a/submodule.h
+++ b/submodule.h
@@ -41,6 +41,12 @@ int parse_submodule_update_strategy(const char *value,
 		struct submodule_update_strategy *dst);
 const char *submodule_strategy_to_string(const struct submodule_update_strategy *s);
 void handle_ignore_submodules_arg(struct diff_options *diffopt, const char *);
+void show_submodule_diff(FILE *f, const char *path,
+		const char *line_prefix,
+		unsigned char one[20], unsigned char two[20],
+		unsigned dirty_submodule, const char *meta,
+		const char *a_prefix, const char *b_prefix,
+		const char *reset);
 void show_submodule_summary(FILE *f, const char *path,
 		const char *line_prefix,
 		unsigned char one[20], unsigned char two[20],
-- 
2.9.2.872.g2dc3c84

Re: [PATCH v4 1/2] diff: add --line-prefix option for passing in a prefix

[Junio C Hamano]

Jacob Keller <jacob.e.keller@intel.com> writes:

>  const char *diff_line_prefix(struct diff_options *opt)
>  {
>  	struct strbuf *msgbuf;
> +
>  	if (!opt->output_prefix)
> -		return "";
> +		if (opt->line_prefix)
> +			return opt->line_prefix;
> +		else
> +			return "";
>  
>  	msgbuf = opt->output_prefix(opt, opt->output_prefix_data);
> +	/* line prefix must be printed before the output_prefix() */
> +	if (opt->line_prefix)
> +		strbuf_insert(msgbuf, 0, opt->line_prefix, strlen(opt->line_prefix));
>  	return msgbuf->buf;
>  }

The result of applying this change leaves the semantics of the
line_prefix field, the output_prefix() callback, and the
output_prefix_length field in the diff_options structure a bit
tricky to reason about.

The code pretends as if the remainder of the system does not even
care about the presence of line_prefix (i.e. output_prefix_length is
not updated), but its only user of output_prefix_length cares, I
think.  It is in diff.c::show_stats() where it auto-computes the
allowed display width for the stat portion:

        if (options->stat_width == -1)
                width = term_columns() - options->output_prefix_length;

The output_prefix_length is initialized to be 0, but when --graph is
in effect, it is set to the width of the graph portion of the output
in the output_prefix callback, diff_output_prefix_callback().

So the above change is clearly wrong in that it needs to add the
number of display columns needed to show opt->line_prefix to the
output_prefix_length, but I wonder if a better "fix" to this is to
get rid of output_prefix_length field from diff_options struct as a
preparatory step.  That would make the bug in this patch disappear.

Perhaps like this.  I do not know if Lucian is still interested in,
or remembers what did for, Git in 2012, but this updates his code
and replaces it with what I hope is an equivalent, so I added him
to the Cc: line.

-- >8 --
Subject: diff.c: remove output_prefix_length field

"diff/log --stat" has a logic that determines the display columns
available for the diffstat part of the output and apportions it for
pathnames and diffstat graph automatically.

5e71a84a (Add output_prefix_length to diff_options, 2012-04-16)
added the output_prefix_length field to diff_options structure to
allow this logic subtract the display columns used for display the
history graph part from the total "terminal width"; this matters
when the "git log --graph -p" option is in use.

The field be set to the number of display columns needed to show the
output from the output_prefix() callback.  Any new output_prefix()
callback must also update the field accordingly, which is error
prone.  As there is only one user of the field, and the user has the
actual value of the prefix string, let's get rid of the field and
have the user count the display width itself.

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

 diff.c  | 2 +-
 diff.h  | 1 -
 graph.c | 2 --
 3 files changed, 1 insertion(+), 4 deletions(-)

diff --git a/diff.c b/diff.c
index b43d3dd..ae069c3 100644
--- a/diff.c
+++ b/diff.c
@@ -1625,7 +1625,7 @@ static void show_stats(struct diffstat_t *data, struct diff_options *options)
 	 */
 
 	if (options->stat_width == -1)
-		width = term_columns() - options->output_prefix_length;
+		width = term_columns() - strlen(line_prefix);
 	else
 		width = options->stat_width ? options->stat_width : 80;
 	number_width = decimal_width(max_change) > number_width ?
diff --git a/diff.h b/diff.h
index 125447b..49e4aaa 100644
--- a/diff.h
+++ b/diff.h
@@ -174,7 +174,6 @@ struct diff_options {
 	diff_format_fn_t format_callback;
 	void *format_callback_data;
 	diff_prefix_fn_t output_prefix;
-	int output_prefix_length;
 	void *output_prefix_data;
 
 	int diff_path_counter;
diff --git a/graph.c b/graph.c
index dd17201..a468038 100644
--- a/graph.c
+++ b/graph.c
@@ -197,7 +197,6 @@ static struct strbuf *diff_output_prefix_callback(struct diff_options *opt, void
 	assert(opt);
 	assert(graph);
 
-	opt->output_prefix_length = graph->width;
 	strbuf_reset(&msgbuf);
 	graph_padding_line(graph, &msgbuf);
 	return &msgbuf;
@@ -245,7 +244,6 @@ struct git_graph *graph_init(struct rev_info *opt)
 	 */
 	opt->diffopt.output_prefix = diff_output_prefix_callback;
 	opt->diffopt.output_prefix_data = graph;
-	opt->diffopt.output_prefix_length = 0;
 
 	return graph;
 }

Re: [PATCH v4 2/2] diff: add SUBMODULE_DIFF format to display submodule diff

[Junio C Hamano]

Jacob Keller <jacob.e.keller@intel.com> writes:

> From: Jacob Keller <jacob.keller@gmail.com>
>
> Teach git-diff and friends a new format for displaying the difference of
> a submodule using git-diff inside the submodule project. This allows
> users to easily see exactly what source changed in a given commit that
> updates the submodule pointer. To do this, remove DIFF_SUBMODULE_LOG bit
> from the diff options, and instead add a new enum type for these
> formats.
>
> Signed-off-by: Jacob Keller <jacob.keller@gmail.com>
> ---
>  Documentation/diff-config.txt  |  3 +-
>  Documentation/diff-options.txt |  6 ++--
>  diff.c                         | 41 ++++++++++++++++----------
>  diff.h                         |  9 +++++-
>  submodule.c                    | 67 ++++++++++++++++++++++++++++++++++++++++++
>  submodule.h                    |  6 ++++
>  6 files changed, 113 insertions(+), 19 deletions(-)

This looks good.

You'd want some tests to make sure that the "--submodule" and the
"--submodule=<format>" command line options and the diff.submodule
configuration variables are parsed correctly (and when combined, the
command line option overrides the configured default), and of course
the machinery does the right thing, with and without "--graph" when
used in "git log".

> diff --git a/Documentation/diff-options.txt b/Documentation/diff-options.txt
> index e7b729f3644f..988068225463 100644
> --- a/Documentation/diff-options.txt
> +++ b/Documentation/diff-options.txt
> @@ -215,8 +215,10 @@ any of those replacements occurred.
>  	the commits in the range like linkgit:git-submodule[1] `summary` does.
>  	Omitting the `--submodule` option or specifying `--submodule=short`,
>  	uses the 'short' format. This format just shows the names of the commits
> -	at the beginning and end of the range.  Can be tweaked via the
> -	`diff.submodule` configuration variable.
> +	at the beginning and end of the range. When `--submodule=diff` is
> +	given, the 'diff' format is used. This format shows the diff between
> +	the old and new submodule commmit from the perspective of the
> +	submodule.  Can be tweaked via the `diff.submodule` configuration variable.

This is carried over from the existing text, but "Can be tweaked
via" sounds a bit wasteful (and strange); "Defaults to" (or "The
default is taken from") is the phrase we seem to use more often.

Thanks.

Re: [PATCH v4 1/2] diff: add --line-prefix option for passing in a prefix

[Jacob Keller]

On Thu, Aug 11, 2016 at 10:22 AM, Junio C Hamano <gitster@pobox.com> wrote:
> -- >8 --
> Subject: diff.c: remove output_prefix_length field
>
> "diff/log --stat" has a logic that determines the display columns
> available for the diffstat part of the output and apportions it for
> pathnames and diffstat graph automatically.
>
> 5e71a84a (Add output_prefix_length to diff_options, 2012-04-16)
> added the output_prefix_length field to diff_options structure to
> allow this logic subtract the display columns used for display the
> history graph part from the total "terminal width"; this matters
> when the "git log --graph -p" option is in use.
>
> The field be set to the number of display columns needed to show the
> output from the output_prefix() callback.  Any new output_prefix()
> callback must also update the field accordingly, which is error
> prone.  As there is only one user of the field, and the user has the
> actual value of the prefix string, let's get rid of the field and
> have the user count the display width itself.
>

Seems correct to me.

Thanks,
Jake

Re: [PATCH v4 2/2] diff: add SUBMODULE_DIFF format to display submodule diff

[Jacob Keller]

On Thu, Aug 11, 2016 at 10:53 AM, Junio C Hamano <gitster@pobox.com> wrote:
> Jacob Keller <jacob.e.keller@intel.com> writes:
>
>> From: Jacob Keller <jacob.keller@gmail.com>
>>
>> Teach git-diff and friends a new format for displaying the difference of
>> a submodule using git-diff inside the submodule project. This allows
>> users to easily see exactly what source changed in a given commit that
>> updates the submodule pointer. To do this, remove DIFF_SUBMODULE_LOG bit
>> from the diff options, and instead add a new enum type for these
>> formats.
>>
>> Signed-off-by: Jacob Keller <jacob.keller@gmail.com>
>> ---
>>  Documentation/diff-config.txt  |  3 +-
>>  Documentation/diff-options.txt |  6 ++--
>>  diff.c                         | 41 ++++++++++++++++----------
>>  diff.h                         |  9 +++++-
>>  submodule.c                    | 67 ++++++++++++++++++++++++++++++++++++++++++
>>  submodule.h                    |  6 ++++
>>  6 files changed, 113 insertions(+), 19 deletions(-)
>
> This looks good.
>
> You'd want some tests to make sure that the "--submodule" and the
> "--submodule=<format>" command line options and the diff.submodule
> configuration variables are parsed correctly (and when combined, the
> command line option overrides the configured default), and of course
> the machinery does the right thing, with and without "--graph" when
> used in "git log".

Yes, I am adding tests now, but I ran into some interesting corner
cases for this, that still need some work.

There's a bunch of issues with cases involving adding a submodule that
isn't stored in .git/modules/etc, which the current tests for
--submodule=log do.

There's also the case of empty trees, which I believe I have resolved
now. Hopefully I can sort these cases correctly.

>
>> diff --git a/Documentation/diff-options.txt b/Documentation/diff-options.txt
>> index e7b729f3644f..988068225463 100644
>> --- a/Documentation/diff-options.txt
>> +++ b/Documentation/diff-options.txt
>> @@ -215,8 +215,10 @@ any of those replacements occurred.
>>       the commits in the range like linkgit:git-submodule[1] `summary` does.
>>       Omitting the `--submodule` option or specifying `--submodule=short`,
>>       uses the 'short' format. This format just shows the names of the commits
>> -     at the beginning and end of the range.  Can be tweaked via the
>> -     `diff.submodule` configuration variable.
>> +     at the beginning and end of the range. When `--submodule=diff` is
>> +     given, the 'diff' format is used. This format shows the diff between
>> +     the old and new submodule commmit from the perspective of the
>> +     submodule.  Can be tweaked via the `diff.submodule` configuration variable.
>
> This is carried over from the existing text, but "Can be tweaked
> via" sounds a bit wasteful (and strange); "Defaults to" (or "The
> default is taken from") is the phrase we seem to use more often.

Probably worth fixing here. WIll do.

Thanks,
Jake

>
> Thanks.

Re: [PATCH v4 2/2] diff: add SUBMODULE_DIFF format to display submodule diff

[Junio C Hamano]

Jacob Keller <jacob.e.keller@intel.com> writes:

> diff --git a/submodule.c b/submodule.c
> index 1b5cdfb7e784..36f8fd00c3ce 100644
> --- a/submodule.c
> +++ b/submodule.c
> @@ -333,6 +333,73 @@ static void print_submodule_summary(struct rev_info *rev, FILE *f,
>  	strbuf_release(&sb);
>  }
>  
> +void show_submodule_diff(FILE *f, const char *path,
> +		const char *line_prefix,
> +		unsigned char one[20], unsigned char two[20],
> +		unsigned dirty_submodule, const char *meta,
> +		const char *a_prefix, const char *b_prefix,
> +		const char *reset)
> +{
> +	struct child_process cp = CHILD_PROCESS_INIT;
> +	struct strbuf sb = STRBUF_INIT;
> +	struct strbuf submodule_git_dir = STRBUF_INIT;
> +	const char *git_dir, *message = NULL;
> +	int create_dirty_diff = 0;
> +	FILE *diff;
> +	char c;

The variables message, diff and c are not used, are they?

Re: [PATCH v4 1/2] diff: add --line-prefix option for passing in a prefix

[Junio C Hamano]

Subject: SQUASH??? clarify the if/{if/else} nesting

Otherwise GCC helpfully warns you.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 diff.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/diff.c b/diff.c
index bfc0a6b..d128b9d 100644
--- a/diff.c
+++ b/diff.c
@@ -1170,11 +1170,12 @@ const char *diff_line_prefix(struct diff_options *opt)
 {
 	struct strbuf *msgbuf;
 
-	if (!opt->output_prefix)
+	if (!opt->output_prefix) {
 		if (opt->line_prefix)
 			return opt->line_prefix;
 		else
 			return "";
+	}
 
 	msgbuf = opt->output_prefix(opt, opt->output_prefix_data);
 	/* line prefix must be printed before the output_prefix() */
-- 
2.9.2-863-g71ed253