Use git_diff_get_stats in example/diff + refactor

This takes the `--stat` and related example options in the example
diff.c program and converts them to use the `git_diff_get_stats`
API which nicely formats stats for you.

I went to add bar-graph scaling to the stats formatter and noticed
that the `git_diff_stats` structure was holding on to all of the
`git_patch` objects.  Unfortunately, each of these objects keeps
the full text of the diff in memory, so this is very expensive.  I
ended up modifying `git_diff_stats` to keep just the data that it
needs to keep and allowed it to release the patches.  Then, I added
width scaling to the output on top of that.

In making the diff example program match 'git diff' output, I ended
up removing an newline from the sumamry output which I then had to
compensate for in the email formatting to match the expectations.

Lastly, I went through and refactored the tests to use a couple of
helper functions and reduce the overall amount of code there.

6 files changed, 340 insertions, 619 deletions

diff --git a/examples/diff.c b/examples/diff.c
index 1dbf85f61..76ac2f311 100644
--- a/examples/diff.c
+++ b/examples/diff.c
@@ -34,10 +34,11 @@ static const char *colors[] = {
 };
 
 enum {
-	OUTPUT_DIFF = 0,
-	OUTPUT_STAT = 1,
-	OUTPUT_SHORTSTAT = 2,
-	OUTPUT_NUMSTAT = 3
+	OUTPUT_DIFF = (1 << 0),
+	OUTPUT_STAT = (1 << 1),
+	OUTPUT_SHORTSTAT = (1 << 2),
+	OUTPUT_NUMSTAT = (1 << 3),
+	OUTPUT_SUMMARY = (1 << 4)
 };
 
 enum {
@@ -137,14 +138,13 @@ int main(int argc, char *argv[])
 
 	/** Generate simple output using libgit2 display helper. */
 
-	switch (o.output) {
-	case OUTPUT_STAT:
-	case OUTPUT_NUMSTAT:
-	case OUTPUT_SHORTSTAT:
+	if (!o.output)
+		o.output = OUTPUT_DIFF;
+
+	if (o.output != OUTPUT_DIFF)
 		diff_print_stats(diff, &o);
-		break;
 
-	case OUTPUT_DIFF:
+	if ((o.output & OUTPUT_DIFF) != 0) {
 		if (o.color >= 0)
 			fputs(colors[0], stdout);
 
@@ -154,10 +154,6 @@ int main(int argc, char *argv[])
 
 		if (o.color >= 0)
 			fputs(colors[0], stdout);
-		break;
-
-	default:
-		usage("Unknown output format", "programmer error");
 	}
 
 	/** Cleanup before exiting. */
@@ -233,8 +229,10 @@ static void parse_opts(struct opts *o, int argc, char *argv[])
 				usage("Only one or two tree identifiers can be provided", NULL);
 		}
 		else if (!strcmp(a, "-p") || !strcmp(a, "-u") ||
-			!strcmp(a, "--patch"))
+				 !strcmp(a, "--patch")) {
+			o->output |= OUTPUT_DIFF;
 			o->format = GIT_DIFF_FORMAT_PATCH;
+		}
 		else if (!strcmp(a, "--cached"))
 			o->cache = CACHE_ONLY;
 		else if (!strcmp(a, "--nocache"))
@@ -273,11 +271,13 @@ static void parse_opts(struct opts *o, int argc, char *argv[])
 		else if (!strcmp(a, "--minimal"))
 			o->diffopts.flags |= GIT_DIFF_MINIMAL;
 		else if (!strcmp(a, "--stat"))
-			o->output = OUTPUT_STAT;
+			o->output |= OUTPUT_STAT;
 		else if (!strcmp(a, "--numstat"))
-			o->output = OUTPUT_NUMSTAT;
+			o->output |= OUTPUT_NUMSTAT;
 		else if (!strcmp(a, "--shortstat"))
-			o->output = OUTPUT_SHORTSTAT;
+			o->output |= OUTPUT_SHORTSTAT;
+		else if (!strcmp(a, "--summary"))
+			o->output |= OUTPUT_SUMMARY;
 		else if (match_uint16_arg(
 				&o->findopts.rename_threshold, &args, "-M") ||
 			match_uint16_arg(
@@ -308,59 +308,30 @@ static void parse_opts(struct opts *o, int argc, char *argv[])
 	}
 }
 
-/** Display diff output with "--numstat" or "--shortstat" */
+/** Display diff output with "--stat", "--numstat", or "--shortstat" */
 static void diff_print_stats(git_diff *diff, struct opts *o)
 {
-	git_patch *patch;
-	size_t d, ndeltas = git_diff_num_deltas(diff);
-	size_t nadditions, ndeletions;
-	long nadditions_sum, ndeletions_sum;
-
-	nadditions_sum = 0;
-	ndeletions_sum = 0;
+	git_diff_stats *stats;
+	git_buf b = GIT_BUF_INIT_CONST(NULL, 0);
+	git_diff_stats_format_t format = 0;
 
-	for (d = 0; d < ndeltas; d++){
-		check_lg2(
-			git_patch_from_diff(&patch, diff, d),
-			"generating patch from diff", NULL);
+	check_lg2(
+		git_diff_get_stats(&stats, diff), "generating stats for diff", NULL);
 
-		check_lg2(
-			git_patch_line_stats(NULL, &nadditions, &ndeletions, patch),
-			"generating the number of additions and deletions", NULL);
+	if (o->output & OUTPUT_STAT)
+		format |= GIT_DIFF_STATS_FULL;
+	if (o->output & OUTPUT_SHORTSTAT)
+		format |= GIT_DIFF_STATS_SHORT;
+	if (o->output & OUTPUT_NUMSTAT)
+		format |= GIT_DIFF_STATS_NUMBER;
+	if (o->output & OUTPUT_SUMMARY)
+		format |= GIT_DIFF_STATS_INCLUDE_SUMMARY;
 
-		if (o->output == OUTPUT_NUMSTAT) {
-			const git_diff_delta *delta = git_patch_get_delta(patch);
-			printf("%ld\t%ld\t%s\n",
-				   (long)nadditions, (long)ndeletions, delta->new_file.path);
-		}
-		else if (o->output == OUTPUT_STAT) {
-			const git_diff_delta *delta = git_patch_get_delta(patch);
-			printf(" %s\t| %ld\t(%ld+ %ld-)\n",
-				   delta->new_file.path, (long)nadditions + (long)ndeletions,
-				   (long)nadditions, (long)ndeletions);
-		}
+	check_lg2(
+		git_diff_stats_to_buf(&b, stats, format, 80), "formatting stats", NULL);
 
-		nadditions_sum += nadditions;
-		ndeletions_sum += ndeletions;
+	fputs(b.ptr, stdout);
 
-		git_patch_free(patch);
-	}
-
-	if (o->output != OUTPUT_NUMSTAT && ndeltas > 0) {
-	    printf(" %ld %s", (long)ndeltas,
-			1 == ndeltas ? "file changed" : "files changed");
-
-	    if (nadditions_sum) {
-			printf(", %ld ",nadditions_sum);
-			printf("%s", 1 == nadditions_sum ? "insertion(+)" : "insertions(+)");
-	    }
-
-	    if (ndeletions_sum) {
-			printf(", %ld ",ndeletions_sum);
-			printf("%s", 1 == ndeletions_sum ? "deletion(-)" : "deletions(-)");
-	    }
-
-	    printf("\n");
-	}
+	git_buf_free(&b);
+	git_diff_stats_free(stats);
 }
-
diff --git a/include/git2/diff.h b/include/git2/diff.h
index c8e1ad143..e5e641a2a 100644
--- a/include/git2/diff.h
+++ b/include/git2/diff.h
@@ -1136,12 +1136,14 @@ GIT_EXTERN(size_t) git_diff_stats_deletions(
  * @param out buffer to store the formatted diff statistics in.
  * @param stats A `git_diff_stats` generated by one of the above functions.
  * @param format Formatting option.
+ * @param width Target width for output (only affects GIT_DIFF_STATS_FULL)
  * @return 0 on success; non-zero on error
  */
 GIT_EXTERN(int) git_diff_stats_to_buf(
 	git_buf *out,
 	const git_diff_stats *stats,
-	git_diff_stats_format_t format);
+	git_diff_stats_format_t format,
+	size_t width);
 
 /**
  * Deallocate a `git_diff_stats`.
diff --git a/src/diff.c b/src/diff.c
index 0d1aed4ad..fd881c6f6 100644
--- a/src/diff.c
+++ b/src/diff.c
@@ -1590,7 +1590,8 @@ int git_diff_format_email(
 
 	if ((error = git_buf_puts(out, "---\n")) < 0 ||
 		(error = git_diff_get_stats(&stats, diff)) < 0 ||
-		(error = git_diff_stats_to_buf(out, stats, format_flags)) < 0 ||
+		(error = git_diff_stats_to_buf(out, stats, format_flags, 0)) < 0 ||
+		(error = git_buf_putc(out, '\n')) < 0 ||
 		(error = git_diff_format_email__append_patches_tobuf(out, diff)) < 0)
 			goto on_error;
 
diff --git a/src/diff_stats.c b/src/diff_stats.c
index bb436bf7b..8a71be894 100644
--- a/src/diff_stats.c
+++ b/src/diff_stats.c
@@ -8,151 +8,123 @@
 #include "vector.h"
 #include "diff.h"
 #include "diff_patch.h"
+#include <math.h>
 
 #define DIFF_RENAME_FILE_SEPARATOR " => "
+#define STATS_FULL_MIN_SCALE 7
+
+typedef struct {
+	size_t insertions;
+	size_t deletions;
+} diff_file_stats;
 
 struct git_diff_stats {
-	git_vector patches;
+	git_diff *diff;
+	diff_file_stats *filestats;
 
 	size_t files_changed;
 	size_t insertions;
 	size_t deletions;
-};
-
-static size_t diff_get_filename_padding(
-	int has_renames,
-	const git_diff_stats *stats)
-{
-	const git_patch *patch = NULL;
-	size_t i, max_padding = 0;
-
-	if (has_renames) {
-		git_vector_foreach(&stats->patches, i, patch) {
-			const git_diff_delta *delta = NULL;
-			size_t len;
-
-			delta = git_patch_get_delta(patch);
-			if (strcmp(delta->old_file.path, delta->new_file.path) == 0)
-				continue;
-
-			if ((len = strlen(delta->old_file.path) + strlen(delta->new_file.path)) > max_padding)
-				max_padding = len;
-		}
-	}
-
-	git_vector_foreach(&stats->patches, i, patch) {
-		const git_diff_delta *delta = NULL;
-		size_t len;
-
-		delta = git_patch_get_delta(patch);
-		len = strlen(delta->new_file.path);
-
-		if (strcmp(delta->old_file.path, delta->new_file.path) != 0)
-			continue;
-
-		if (len > max_padding)
-			max_padding = len;
-	}
+	size_t renames;
 
-	return max_padding;
-}
+	size_t max_name;
+	size_t max_filestat;
+	int max_digits;
+};
 
 int git_diff_file_stats__full_to_buf(
 	git_buf *out,
-	size_t max_padding,
-	int has_renames,
-	const git_patch *patch)
+	const git_diff_delta *delta,
+	const diff_file_stats *filestat,
+	const git_diff_stats *stats,
+	double scale_to)
 {
 	const char *old_path = NULL, *new_path = NULL;
-	const git_diff_delta *delta = NULL;
 	size_t padding, old_size, new_size;
-	int error;
-
-	delta = git_patch_get_delta(patch);
 
 	old_path = delta->old_file.path;
 	new_path = delta->new_file.path;
 	old_size = delta->old_file.size;
 	new_size = delta->new_file.size;
 
-	if ((error = git_buf_printf(out, " %s", old_path)) < 0)
+	if (git_buf_printf(out, " %s", old_path) < 0)
 		goto on_error;
 
 	if (strcmp(old_path, new_path) != 0) {
-		padding = max_padding - strlen(old_path) - strlen(new_path);
+		padding = stats->max_name - strlen(old_path) - strlen(new_path);
 
-		if ((error = git_buf_printf(out, DIFF_RENAME_FILE_SEPARATOR "%s", new_path)) < 0)
+		if (git_buf_printf(out, DIFF_RENAME_FILE_SEPARATOR "%s", new_path) < 0)
 			goto on_error;
-	}
-	else {
-		padding = max_padding - strlen(old_path);
+	} else {
+		padding = stats->max_name - strlen(old_path);
 
-		if (has_renames)
+		if (stats->renames > 0)
 			padding += strlen(DIFF_RENAME_FILE_SEPARATOR);
 	}
 
-	if ((error = git_buf_putcn(out, ' ', padding)) < 0 ||
-		(error = git_buf_puts(out, " | ")) < 0)
-			goto on_error;
+	if (git_buf_putcn(out, ' ', padding) < 0 ||
+		git_buf_puts(out, " | ") < 0)
+		goto on_error;
 
 	if (delta->flags & GIT_DIFF_FLAG_BINARY) {
-		if ((error = git_buf_printf(out, "Bin %" PRIuZ " -> %" PRIuZ " bytes", old_size, new_size)) < 0)
+		if (git_buf_printf(out,
+				"Bin %" PRIuZ " -> %" PRIuZ " bytes", old_size, new_size) < 0)
 			goto on_error;
 	}
 	else {
-		size_t insertions, deletions;
-
-		if ((error = git_patch_line_stats(NULL, &insertions, &deletions, patch)) < 0)
+		if (git_buf_printf(out,
+				"%*" PRIuZ, stats->max_digits,
+				filestat->insertions + filestat->deletions) < 0)
 			goto on_error;
 
-		if ((error = git_buf_printf(out, "%" PRIuZ, insertions + deletions)) < 0)
-			goto on_error;
+		if (filestat->insertions || filestat->deletions) {
+			if (git_buf_putc(out, ' ') < 0)
+				goto on_error;
 
-		if (insertions || deletions) {
-			if ((error = git_buf_putc(out, ' ')) < 0 ||
-				(error = git_buf_putcn(out, '+', insertions)) < 0 ||
-				(error = git_buf_putcn(out, '-', deletions)) < 0)
+			if (scale_to <= 0) {
+				if (git_buf_putcn(out, '+', filestat->insertions) < 0 ||
+					git_buf_putcn(out, '-', filestat->deletions) < 0)
 					goto on_error;
+			} else {
+				size_t total = filestat->insertions + filestat->deletions;
+				double full = round(total * scale_to / stats->max_filestat);
+				size_t plus = full * filestat->insertions / total;
+				size_t minus = (size_t)full - plus;
+
+				if (git_buf_putcn(out, '+', max(plus,  1)) < 0 ||
+					git_buf_putcn(out, '-', max(minus, 1)) < 0)
+					goto on_error;
+			}
 		}
 	}
 
-	error = git_buf_putc(out, '\n');
+	git_buf_putc(out, '\n');
 
 on_error:
-	return error;
+	return (git_buf_oom(out) ? -1 : 0);
 }
 
 int git_diff_file_stats__number_to_buf(
 	git_buf *out,
-	const git_patch *patch)
+	const git_diff_delta *delta,
+	const diff_file_stats *filestats)
 {
-	const git_diff_delta *delta = NULL;
-	const char *path = NULL;
-	size_t insertions, deletions;
 	int error;
-
-	delta = git_patch_get_delta(patch);
-	path = delta->new_file.path;
-
-	if ((error = git_patch_line_stats(NULL, &insertions, &deletions, patch)) < 0)
-		return error;
+	const char *path = delta->new_file.path;
 
 	if (delta->flags & GIT_DIFF_FLAG_BINARY)
 		error = git_buf_printf(out, "%-8c" "%-8c" "%s\n", '-', '-', path);
 	else
-		error = git_buf_printf(out, "%-8" PRIuZ "%-8" PRIuZ "%s\n", insertions, deletions, path);
+		error = git_buf_printf(out, "%-8" PRIuZ "%-8" PRIuZ "%s\n",
+			filestats->insertions, filestats->deletions, path);
 
 	return error;
 }
 
 int git_diff_file_stats__summary_to_buf(
 	git_buf *out,
-	const git_patch *patch)
+	const git_diff_delta *delta)
 {
-	const git_diff_delta *delta = NULL;
-
-	delta = git_patch_get_delta(patch);
-
 	if (delta->old_file.mode != delta->new_file.mode) {
 		if (delta->old_file.mode == 0) {
 			git_buf_printf(out, " create mode %06o %s\n",
@@ -171,39 +143,6 @@ int git_diff_file_stats__summary_to_buf(
 	return 0;
 }
 
-int git_diff_stats__has_renames(
-	const git_diff_stats *stats)
-{
-	git_patch *patch = NULL;
-	size_t i;
-
-	git_vector_foreach(&stats->patches, i, patch) {
-		const git_diff_delta *delta = git_patch_get_delta(patch);
-
-		if (strcmp(delta->old_file.path, delta->new_file.path) != 0) {
-			return 1;
-		}
-	}
-
-	return 0;
-}
-
-int git_diff_stats__add_file_stats(
-	git_diff_stats *stats,
-	git_patch *patch)
-{
-	const git_diff_delta *delta = NULL;
-	int error = 0;
-
-	if ((delta = git_patch_get_delta(patch)) == NULL)
-		return -1;
-
-	if ((error = git_vector_insert(&stats->patches, patch)) < 0)
-		return error;
-
-	return error;
-}
-
 int git_diff_get_stats(
 	git_diff_stats **out,
 	git_diff *diff)
@@ -220,35 +159,60 @@ int git_diff_get_stats(
 
 	deltas = git_diff_num_deltas(diff);
 
-	for (i = 0; i < deltas; ++i) {
+	stats->filestats = git__calloc(deltas, sizeof(diff_file_stats));
+	if (!stats->filestats) {
+		git__free(stats);
+		return -1;
+	}
+
+	stats->diff = diff;
+	GIT_REFCOUNT_INC(diff);
+
+	for (i = 0; i < deltas && !error; ++i) {
 		git_patch *patch = NULL;
-		size_t add, remove;
+		size_t add = 0, remove = 0, namelen;
+		const git_diff_delta *delta;
 
 		if ((error = git_patch_from_diff(&patch, diff, i)) < 0)
-			goto on_error;
+			break;
 
-		if ((error = git_patch_line_stats(NULL, &add, &remove, patch)) < 0 ||
-			(error = git_diff_stats__add_file_stats(stats, patch)) < 0) {
-			git_patch_free(patch);
-			goto on_error;
+		/* keep a count of renames because it will affect formatting */
+		delta = git_patch_get_delta(patch);
+
+		namelen = strlen(delta->new_file.path);
+		if (strcmp(delta->old_file.path, delta->new_file.path) != 0) {
+			namelen += strlen(delta->old_file.path);
+			stats->renames++;
 		}
 
+		/* and, of course, count the line stats */
+		error = git_patch_line_stats(NULL, &add, &remove, patch);
+
+		git_patch_free(patch);
+
+		stats->filestats[i].insertions = add;
+		stats->filestats[i].deletions = remove;
+
 		total_insertions += add;
 		total_deletions += remove;
+
+		if (stats->max_name < namelen)
+			stats->max_name = namelen;
+		if (stats->max_filestat < add + remove)
+			stats->max_filestat = add + remove;
 	}
 
 	stats->files_changed = deltas;
 	stats->insertions = total_insertions;
 	stats->deletions = total_deletions;
+	stats->max_digits = (int)ceil(log10(stats->max_filestat + 1));
 
-	*out = stats;
-
-	goto done;
-
-on_error:
-	git_diff_stats_free(stats);
+	if (error < 0) {
+		git_diff_stats_free(stats);
+		stats = NULL;
+	}
 
-done:
+	*out = stats;
 	return error;
 }
 
@@ -279,48 +243,68 @@ size_t git_diff_stats_deletions(
 int git_diff_stats_to_buf(
 	git_buf *out,
 	const git_diff_stats *stats,
-	git_diff_stats_format_t format)
+	git_diff_stats_format_t format,
+	size_t width)
 {
-	git_patch *patch = NULL;
+	int error = 0;
 	size_t i;
-	int has_renames = 0, error = 0;
+	const git_diff_delta *delta;
 
 	assert(out && stats);
 
-	/* check if we have renames, it affects the padding */
-	has_renames = git_diff_stats__has_renames(stats);
-
-	git_vector_foreach(&stats->patches, i, patch) {
-		if (format & GIT_DIFF_STATS_FULL) {
-			size_t max_padding = diff_get_filename_padding(has_renames, stats);
+	if (format & GIT_DIFF_STATS_NUMBER) {
+		for (i = 0; i < stats->files_changed; ++i) {
+			if ((delta = git_diff_get_delta(stats->diff, i)) == NULL)
+				continue;
 
-			error = git_diff_file_stats__full_to_buf(out, max_padding, has_renames, patch);
+			error = git_diff_file_stats__number_to_buf(
+				out, delta, &stats->filestats[i]);
+			if (error < 0)
+				return error;
 		}
-		else if (format & GIT_DIFF_STATS_NUMBER) {
-			error = git_diff_file_stats__number_to_buf(out, patch);
+	}
+
+	if (format & GIT_DIFF_STATS_FULL) {
+		double scale_to = -1;
+		if (width > 0) {
+			if (width > stats->max_name + stats->max_digits + 5)
+				scale_to = width - (stats->max_name + stats->max_digits + 5);
+			if (scale_to < STATS_FULL_MIN_SCALE)
+				scale_to = STATS_FULL_MIN_SCALE;
 		}
 
-		if (error < 0)
-			return error;
+		for (i = 0; i < stats->files_changed; ++i) {
+			if ((delta = git_diff_get_delta(stats->diff, i)) == NULL)
+				continue;
+
+			error = git_diff_file_stats__full_to_buf(
+				out, delta, &stats->filestats[i], stats, scale_to);
+			if (error < 0)
+				return error;
+		}
 	}
 
 	if (format & GIT_DIFF_STATS_FULL || format & GIT_DIFF_STATS_SHORT) {
-		error = git_buf_printf(out, " %" PRIuZ " file%s changed, %" PRIuZ " insertions(+), %" PRIuZ " deletions(-)\n",
-					stats->files_changed, stats->files_changed > 1 ? "s" : "",
-					stats->insertions, stats->deletions);
+		error = git_buf_printf(
+			out, " %" PRIuZ " file%s changed, %" PRIuZ
+			" insertion%s(+), %" PRIuZ " deletion%s(-)\n",
+			stats->files_changed, stats->files_changed != 1 ? "s" : "",
+			stats->insertions, stats->insertions != 1 ? "s" : "",
+			stats->deletions, stats->deletions != 1 ? "s" : "");
 
 		if (error < 0)
 			return error;
 	}
 
 	if (format & GIT_DIFF_STATS_INCLUDE_SUMMARY) {
-		git_vector_foreach(&stats->patches, i, patch) {
-			if ((error = git_diff_file_stats__summary_to_buf(out, patch)) < 0)
+		for (i = 0; i < stats->files_changed; ++i) {
+			if ((delta = git_diff_get_delta(stats->diff, i)) == NULL)
+				continue;
+
+			error = git_diff_file_stats__summary_to_buf(out, delta);
+			if (error < 0)
 				return error;
 		}
-
-		if (git_vector_length(&stats->patches) > 0)
-			git_buf_putc(out, '\n');
 	}
 
 	return error;
@@ -328,16 +312,11 @@ int git_diff_stats_to_buf(
 
 void git_diff_stats_free(git_diff_stats *stats)
 {
-	size_t i;
-	git_patch *patch;
-
 	if (stats == NULL)
 		return;
 
-	git_vector_foreach(&stats->patches, i, patch)
-		git_patch_free(patch);
-
-	git_vector_free(&stats->patches);
+	git_diff_free(stats->diff); /* bumped refcount in constructor */
+	git__free(stats->filestats);
 	git__free(stats);
 }
 
diff --git a/tests/diff/format_email.c b/tests/diff/format_email.c
index 3260fdea8..18ad99bd5 100644
--- a/tests/diff/format_email.c
+++ b/tests/diff/format_email.c
@@ -17,15 +17,44 @@ void test_diff_format_email__cleanup(void)
 	cl_git_sandbox_cleanup();
 }
 
-void test_diff_format_email__simple(void)
+static void assert_email_match(
+	const char *expected,
+	const char *oidstr,
+	git_diff_format_email_options *opts)
 {
 	git_oid oid;
 	git_commit *commit = NULL;
 	git_diff *diff = NULL;
-	git_diff_format_email_options opts = GIT_DIFF_FORMAT_EMAIL_OPTIONS_INIT;
 	git_buf buf = GIT_BUF_INIT;
 
-	const char *email = 
+	git_oid_fromstr(&oid, oidstr);
+
+	cl_git_pass(git_commit_lookup(&commit, repo, &oid));
+
+	opts->id = git_commit_id(commit);
+	opts->author = git_commit_author(commit);
+	if (!opts->summary)
+		opts->summary = git_commit_summary(commit);
+
+	cl_git_pass(git_diff__commit(&diff, repo, commit, NULL));
+	cl_git_pass(git_diff_format_email(&buf, diff, opts));
+
+	cl_assert_equal_s(expected, git_buf_cstr(&buf));
+	git_buf_clear(&buf);
+
+	cl_git_pass(git_diff_commit_as_email(
+		&buf, repo, commit, 1, 1, opts->flags, NULL));
+	cl_assert_equal_s(expected, git_buf_cstr(&buf));
+
+	git_diff_free(diff);
+	git_commit_free(commit);
+	git_buf_free(&buf);
+}
+
+void test_diff_format_email__simple(void)
+{
+	git_diff_format_email_options opts = GIT_DIFF_FORMAT_EMAIL_OPTIONS_INIT;
+	const char *email =
 	"From 9264b96c6d104d0e07ae33d3007b6a48246c6f92 Mon Sep 17 00:00:00 2001\n" \
 	"From: Jacques Germishuys <jacquesg@striata.com>\n" \
 	"Date: Wed, 9 Apr 2014 20:57:01 +0200\n" \
@@ -64,25 +93,8 @@ void test_diff_format_email__simple(void)
 	"libgit2 " LIBGIT2_VERSION "\n" \
 	"\n";
 
-	git_oid_fromstr(&oid, "9264b96c6d104d0e07ae33d3007b6a48246c6f92");
-
-	cl_git_pass(git_commit_lookup(&commit, repo, &oid));
-
-	opts.id = git_commit_id(commit);
-	opts.author = git_commit_author(commit);
-	opts.summary = git_commit_summary(commit);
-
-	cl_git_pass(git_diff__commit(&diff, repo, commit, NULL));
-	cl_git_pass(git_diff_format_email(&buf, diff, &opts));
-	cl_assert(strcmp(git_buf_cstr(&buf), email) == 0);
-
-	git_buf_clear(&buf);
-	cl_git_pass(git_diff_commit_as_email(&buf, repo, commit, 1, 1, 0, NULL));
-	cl_assert(strcmp(git_buf_cstr(&buf), email) == 0);
-
-	git_diff_free(diff);
-	git_commit_free(commit);
-	git_buf_free(&buf);
+	assert_email_match(
+		email, "9264b96c6d104d0e07ae33d3007b6a48246c6f92", &opts);
 }
 
 void test_diff_format_email__multiple(void)
@@ -90,10 +102,10 @@ void test_diff_format_email__multiple(void)
 	git_oid oid;
 	git_commit *commit = NULL;
 	git_diff *diff = NULL;
-	git_diff_format_email_options opts = GIT_DIFF_FORMAT_EMAIL_OPTIONS_INIT;
+ 	git_diff_format_email_options opts = GIT_DIFF_FORMAT_EMAIL_OPTIONS_INIT;
 	git_buf buf = GIT_BUF_INIT;
 
-	const char *email = 
+	const char *email =
 	"From 10808fe9c9be5a190c0ba68d1a002233fb363508 Mon Sep 17 00:00:00 2001\n" \
 	"From: Jacques Germishuys <jacquesg@striata.com>\n" \
 	"Date: Thu, 10 Apr 2014 19:37:05 +0200\n" \
@@ -167,6 +179,7 @@ void test_diff_format_email__multiple(void)
 	"libgit2 " LIBGIT2_VERSION "\n" \
 	"\n";
 
+
 	git_oid_fromstr(&oid, "10808fe9c9be5a190c0ba68d1a002233fb363508");
 	cl_git_pass(git_commit_lookup(&commit, repo, &oid));
 
@@ -196,7 +209,7 @@ void test_diff_format_email__multiple(void)
 	cl_git_pass(git_diff__commit(&diff, repo, commit, NULL));
 	cl_git_pass(git_diff_format_email(&buf, diff, &opts));
 
-	cl_assert(strcmp(git_buf_cstr(&buf), email) == 0);
+	cl_assert_equal_s(email, git_buf_cstr(&buf));
 
 	git_diff_free(diff);
 	git_commit_free(commit);
@@ -205,13 +218,8 @@ void test_diff_format_email__multiple(void)
 
 void test_diff_format_email__exclude_marker(void)
 {
-	git_oid oid;
-	git_commit *commit = NULL;
-	git_diff *diff = NULL;
 	git_diff_format_email_options opts = GIT_DIFF_FORMAT_EMAIL_OPTIONS_INIT;
-	git_buf buf = GIT_BUF_INIT;
-
-	const char *email = 
+	const char *email =
 	"From 9264b96c6d104d0e07ae33d3007b6a48246c6f92 Mon Sep 17 00:00:00 2001\n" \
 	"From: Jacques Germishuys <jacquesg@striata.com>\n" \
 	"Date: Wed, 9 Apr 2014 20:57:01 +0200\n" \
@@ -250,27 +258,10 @@ void test_diff_format_email__exclude_marker(void)
 	"libgit2 " LIBGIT2_VERSION "\n" \
 	"\n";
 
-	git_oid_fromstr(&oid, "9264b96c6d104d0e07ae33d3007b6a48246c6f92");
-	cl_git_pass(git_commit_lookup(&commit, repo, &oid));
-
-	opts.id = git_commit_id(commit);
-	opts.author = git_commit_author(commit);
-	opts.summary = git_commit_summary(commit);
-
 	opts.flags |= GIT_DIFF_FORMAT_EMAIL_EXCLUDE_SUBJECT_PATCH_MARKER;
 
-	cl_git_pass(git_diff__commit(&diff, repo, commit, NULL));
-	cl_git_pass(git_diff_format_email(&buf, diff, &opts));
-	cl_assert(strcmp(git_buf_cstr(&buf), email) == 0);
-
-	git_buf_clear(&buf);
-	cl_git_pass(git_diff_commit_as_email(&buf, repo, commit, 1, 1,
-		GIT_DIFF_FORMAT_EMAIL_EXCLUDE_SUBJECT_PATCH_MARKER, NULL));
-	cl_assert(strcmp(git_buf_cstr(&buf), email) == 0);
-
-	git_diff_free(diff);
-	git_commit_free(commit);
-	git_buf_free(&buf);
+	assert_email_match(
+		email, "9264b96c6d104d0e07ae33d3007b6a48246c6f92", &opts);
 }
 
 void test_diff_format_email__invalid_no(void)
@@ -303,13 +294,8 @@ void test_diff_format_email__invalid_no(void)
 
 void test_diff_format_email__mode_change(void)
 {
-	git_oid oid;
-	git_commit *commit = NULL;
-	git_diff *diff = NULL;
 	git_diff_format_email_options opts = GIT_DIFF_FORMAT_EMAIL_OPTIONS_INIT;
-	git_buf buf = GIT_BUF_INIT;
-
-	const char *email = 
+	const char *email =
 	"From 7ade76dd34bba4733cf9878079f9fd4a456a9189 Mon Sep 17 00:00:00 2001\n" \
 	"From: Jacques Germishuys <jacquesg@striata.com>\n" \
 	"Date: Thu, 10 Apr 2014 10:05:03 +0200\n" \
@@ -330,36 +316,14 @@ void test_diff_format_email__mode_change(void)
 	"libgit2 " LIBGIT2_VERSION "\n" \
 	"\n";
 
-	git_oid_fromstr(&oid, "7ade76dd34bba4733cf9878079f9fd4a456a9189");
-
-	cl_git_pass(git_commit_lookup(&commit, repo, &oid));
-
-	opts.id = git_commit_id(commit);
-	opts.author = git_commit_author(commit);
-	opts.summary = git_commit_summary(commit);
-
-	cl_git_pass(git_diff__commit(&diff, repo, commit, NULL));
-	cl_git_pass(git_diff_format_email(&buf, diff, &opts));
-	cl_assert(strcmp(git_buf_cstr(&buf), email) == 0);
-
-	git_buf_clear(&buf);
-	cl_git_pass(git_diff_commit_as_email(&buf, repo, commit, 1, 1, 0, NULL));
-	cl_assert(strcmp(git_buf_cstr(&buf), email) == 0);
-
-	git_diff_free(diff);
-	git_commit_free(commit);
-	git_buf_free(&buf);
+	assert_email_match(
+		email, "7ade76dd34bba4733cf9878079f9fd4a456a9189", &opts);
 }
 
 void test_diff_format_email__rename_add_remove(void)
 {
-	git_oid oid;
-	git_commit *commit = NULL;
-	git_diff *diff = NULL;
 	git_diff_format_email_options opts = GIT_DIFF_FORMAT_EMAIL_OPTIONS_INIT;
-	git_buf buf = GIT_BUF_INIT;
-
-	const char *email = 
+	const char *email =
 	"From 6e05acc5a5dab507d91a0a0cc0fb05a3dd98892d Mon Sep 17 00:00:00 2001\n" \
 	"From: Jacques Germishuys <jacquesg@striata.com>\n" \
 	"Date: Wed, 9 Apr 2014 21:15:56 +0200\n" \
@@ -422,35 +386,13 @@ void test_diff_format_email__rename_add_remove(void)
 	"libgit2 " LIBGIT2_VERSION "\n" \
 	"\n";
 
-	git_oid_fromstr(&oid, "6e05acc5a5dab507d91a0a0cc0fb05a3dd98892d");
-
-	cl_git_pass(git_commit_lookup(&commit, repo, &oid));
-
-	opts.id = git_commit_id(commit);
-	opts.author = git_commit_author(commit);
-	opts.summary = git_commit_summary(commit);
-
-	cl_git_pass(git_diff__commit(&diff, repo, commit, NULL));
-	cl_git_pass(git_diff_format_email(&buf, diff, &opts));
-	cl_assert(strcmp(git_buf_cstr(&buf), email) == 0);
-
-	git_buf_clear(&buf);
-	cl_git_pass(git_diff_commit_as_email(&buf, repo, commit, 1, 1, 0, NULL));
-	cl_assert(strcmp(git_buf_cstr(&buf), email) == 0);
-
-	git_diff_free(diff);
-	git_commit_free(commit);
-	git_buf_free(&buf);
+	assert_email_match(
+		email, "6e05acc5a5dab507d91a0a0cc0fb05a3dd98892d", &opts);
 }
 
 void test_diff_format_email__multiline_summary(void)
 {
-	git_oid oid;
-	git_commit *commit = NULL;
-	git_diff *diff = NULL;
 	git_diff_format_email_options opts = GIT_DIFF_FORMAT_EMAIL_OPTIONS_INIT;
-	git_buf buf = GIT_BUF_INIT;
-
 	const char *email =
 	"From 9264b96c6d104d0e07ae33d3007b6a48246c6f92 Mon Sep 17 00:00:00 2001\n" \
 	"From: Jacques Germishuys <jacquesg@striata.com>\n" \
@@ -490,36 +432,15 @@ void test_diff_format_email__multiline_summary(void)
 	"libgit2 " LIBGIT2_VERSION "\n" \
 	"\n";
 
-	git_oid_fromstr(&oid, "9264b96c6d104d0e07ae33d3007b6a48246c6f92");
-
-	cl_git_pass(git_commit_lookup(&commit, repo, &oid));
-
-	opts.id = git_commit_id(commit);
-	opts.author = git_commit_author(commit);
 	opts.summary = "Modify some content\nSome extra stuff here";
 
-	cl_git_pass(git_diff__commit(&diff, repo, commit, NULL));
-	cl_git_pass(git_diff_format_email(&buf, diff, &opts));
-	cl_assert(strcmp(git_buf_cstr(&buf), email) == 0);
-
-	git_buf_clear(&buf);
-	cl_git_pass(git_diff_commit_as_email(&buf, repo, commit, 1, 1, 0, NULL));
-	cl_assert(strcmp(git_buf_cstr(&buf), email) == 0);
-
-	git_diff_free(diff);
-	git_commit_free(commit);
-	git_buf_free(&buf);
+	assert_email_match(
+		email, "9264b96c6d104d0e07ae33d3007b6a48246c6f92", &opts);
 }
 
 void test_diff_format_email__binary(void)
 {
-	git_oid oid;
-	git_commit *commit = NULL;
-	git_diff *diff = NULL;
 	git_diff_format_email_options opts = GIT_DIFF_FORMAT_EMAIL_OPTIONS_INIT;
-	git_buf buf = GIT_BUF_INIT;
-
-	/* TODO: Actually 0 bytes here should be 5!. Seems like we don't load the new content for binary files? */
 	const char *email =
 	"From 8d7523f6fcb2404257889abe0d96f093d9f524f9 Mon Sep 17 00:00:00 2001\n" \
 	"From: Jacques Germishuys <jacquesg@striata.com>\n" \
@@ -536,21 +457,11 @@ void test_diff_format_email__binary(void)
 	"--\n" \
 	"libgit2 " LIBGIT2_VERSION "\n" \
 	"\n";
+	/* TODO: Actually 0 bytes here should be 5!. Seems like we don't load the new content for binary files? */
 
-	git_oid_fromstr(&oid, "8d7523f6fcb2404257889abe0d96f093d9f524f9");
-
-	cl_git_pass(git_commit_lookup(&commit, repo, &oid));
-
-	opts.id = git_commit_id(commit);
-	opts.author = git_commit_author(commit);
 	opts.summary = "Modified binary file";
 
-	cl_git_pass(git_diff__commit(&diff, repo, commit, NULL));
-	cl_git_pass(git_diff_format_email(&buf, diff, &opts));
-	cl_assert(strcmp(git_buf_cstr(&buf), email) == 0);
-
-	git_diff_free(diff);
-	git_commit_free(commit);
-	git_buf_free(&buf);
+	assert_email_match(
+		email, "8d7523f6fcb2404257889abe0d96f093d9f524f9", &opts);
 }
 
diff --git a/tests/diff/stats.c b/tests/diff/stats.c
index 131b7681d..055019f69 100644
--- a/tests/diff/stats.c
+++ b/tests/diff/stats.c
@@ -5,246 +5,173 @@
 #include "commit.h"
 #include "diff.h"
 
-static git_repository *repo;
+static git_repository *_repo;
+static git_diff_stats *_stats;
 
 void test_diff_stats__initialize(void)
 {
-	repo = cl_git_sandbox_init("diff_format_email");
+	_repo = cl_git_sandbox_init("diff_format_email");
 }
 
 void test_diff_stats__cleanup(void)
 {
+	git_diff_stats_free(_stats); _stats = NULL;
 	cl_git_sandbox_cleanup();
 }
 
-void test_diff_stats__stat(void)
+static void diff_stats_from_commit_oid(
+	git_diff_stats **stats, const char *oidstr, bool rename)
 {
 	git_oid oid;
-	git_commit *commit = NULL;
-	git_diff *diff = NULL;
-	git_diff_stats *stats = NULL;
-	git_buf buf = GIT_BUF_INIT;
+	git_commit *commit;
+	git_diff *diff;
+
+	git_oid_fromstr(&oid, oidstr);
+	cl_git_pass(git_commit_lookup(&commit, _repo, &oid));
+	cl_git_pass(git_diff__commit(&diff, _repo, commit, NULL));
+	if (rename)
+		cl_git_pass(git_diff_find_similar(diff, NULL));
+	cl_git_pass(git_diff_get_stats(stats, diff));
+
+	git_diff_free(diff);
+	git_commit_free(commit);
+}
 
+void test_diff_stats__stat(void)
+{
+	git_buf buf = GIT_BUF_INIT;
 	const char *stat =
 	" file1.txt | 8 +++++---\n" \
 	" 1 file changed, 5 insertions(+), 3 deletions(-)\n";
 
-	git_oid_fromstr(&oid, "9264b96c6d104d0e07ae33d3007b6a48246c6f92");
+	diff_stats_from_commit_oid(
+		&_stats, "9264b96c6d104d0e07ae33d3007b6a48246c6f92", false);
 
-	cl_git_pass(git_commit_lookup(&commit, repo, &oid));
-	cl_git_pass(git_diff__commit(&diff, repo, commit, NULL));
+	cl_assert_equal_sz(1, git_diff_stats_files_changed(_stats));
+	cl_assert_equal_sz(5, git_diff_stats_insertions(_stats));
+	cl_assert_equal_sz(3, git_diff_stats_deletions(_stats));
 
-	cl_git_pass(git_diff_get_stats(&stats, diff));
-	cl_assert(git_diff_stats_files_changed(stats) == 1);
-	cl_assert(git_diff_stats_insertions(stats) == 5);
-	cl_assert(git_diff_stats_deletions(stats) == 3);
-
-	cl_git_pass(git_diff_stats_to_buf(&buf, stats, GIT_DIFF_STATS_FULL));
+	cl_git_pass(git_diff_stats_to_buf(&buf, _stats, GIT_DIFF_STATS_FULL, 0));
 	cl_assert(strcmp(git_buf_cstr(&buf), stat) == 0);
-
-	git_diff_stats_free(stats);
-	git_diff_free(diff);
-	git_commit_free(commit);
 	git_buf_free(&buf);
 }
 
 void test_diff_stats__multiple_hunks(void)
 {
-	git_oid oid;
-	git_commit *commit = NULL;
-	git_diff *diff = NULL;
-	git_diff_stats *stats = NULL;
 	git_buf buf = GIT_BUF_INIT;
-
 	const char *stat =
 	" file2.txt | 5 +++--\n" \
 	" file3.txt | 6 ++++--\n" \
 	" 2 files changed, 7 insertions(+), 4 deletions(-)\n";
 
-	git_oid_fromstr(&oid, "cd471f0d8770371e1bc78bcbb38db4c7e4106bd2");
-
-	cl_git_pass(git_commit_lookup(&commit, repo, &oid));
-	cl_git_pass(git_diff__commit(&diff, repo, commit, NULL));
+	diff_stats_from_commit_oid(
+		&_stats, "cd471f0d8770371e1bc78bcbb38db4c7e4106bd2", false);
 
-	cl_git_pass(git_diff_get_stats(&stats, diff));
-	cl_assert(git_diff_stats_files_changed(stats) == 2);
-	cl_assert(git_diff_stats_insertions(stats) == 7);
-	cl_assert(git_diff_stats_deletions(stats) == 4);
+	cl_assert_equal_sz(2, git_diff_stats_files_changed(_stats));
+	cl_assert_equal_sz(7, git_diff_stats_insertions(_stats));
+	cl_assert_equal_sz(4, git_diff_stats_deletions(_stats));
 
-	cl_git_pass(git_diff_stats_to_buf(&buf, stats, GIT_DIFF_STATS_FULL));
-	cl_assert(strcmp(git_buf_cstr(&buf), stat) == 0);
-
-	git_diff_stats_free(stats);
-	git_diff_free(diff);
-	git_commit_free(commit);
+	cl_git_pass(git_diff_stats_to_buf(&buf, _stats, GIT_DIFF_STATS_FULL, 0));
+	cl_assert_equal_s(stat, git_buf_cstr(&buf));
 	git_buf_free(&buf);
 }
 
 void test_diff_stats__numstat(void)
 {
-	git_oid oid;
-	git_commit *commit = NULL;
-	git_diff *diff = NULL;
-	git_diff_stats *stats = NULL;
 	git_buf buf = GIT_BUF_INIT;
-
 	const char *stat =
 	"3       2       file2.txt\n"
 	"4       2       file3.txt\n";
 
-	git_oid_fromstr(&oid, "cd471f0d8770371e1bc78bcbb38db4c7e4106bd2");
-
-	cl_git_pass(git_commit_lookup(&commit, repo, &oid));
-	cl_git_pass(git_diff__commit(&diff, repo, commit, NULL));
-
-	cl_git_pass(git_diff_get_stats(&stats, diff));
-
-	cl_git_pass(git_diff_stats_to_buf(&buf, stats, GIT_DIFF_STATS_NUMBER));
-	cl_assert(strcmp(git_buf_cstr(&buf), stat) == 0);
+	diff_stats_from_commit_oid(
+		&_stats, "cd471f0d8770371e1bc78bcbb38db4c7e4106bd2", false);
 
-	git_diff_stats_free(stats);
-	git_diff_free(diff);
-	git_commit_free(commit);
+	cl_git_pass(git_diff_stats_to_buf(&buf, _stats, GIT_DIFF_STATS_NUMBER, 0));
+	cl_assert_equal_s(stat, git_buf_cstr(&buf));
 	git_buf_free(&buf);
 }
 
 void test_diff_stats__shortstat(void)
 {
-	git_oid oid;
-	git_commit *commit = NULL;
-	git_diff *diff = NULL;
-	git_diff_stats *stats = NULL;
 	git_buf buf = GIT_BUF_INIT;
-
 	const char *stat =
 	" 1 file changed, 5 insertions(+), 3 deletions(-)\n";
 
-	git_oid_fromstr(&oid, "9264b96c6d104d0e07ae33d3007b6a48246c6f92");
-
-	cl_git_pass(git_commit_lookup(&commit, repo, &oid));
-	cl_git_pass(git_diff__commit(&diff, repo, commit, NULL));
+	diff_stats_from_commit_oid(
+		&_stats, "9264b96c6d104d0e07ae33d3007b6a48246c6f92", false);
 
-	cl_git_pass(git_diff_get_stats(&stats, diff));
-	cl_assert(git_diff_stats_files_changed(stats) == 1);
-	cl_assert(git_diff_stats_insertions(stats) == 5);
-	cl_assert(git_diff_stats_deletions(stats) == 3);
+	cl_assert_equal_sz(1, git_diff_stats_files_changed(_stats));
+	cl_assert_equal_sz(5, git_diff_stats_insertions(_stats));
+	cl_assert_equal_sz(3, git_diff_stats_deletions(_stats));
 
-	cl_git_pass(git_diff_stats_to_buf(&buf, stats, GIT_DIFF_STATS_SHORT));
-	cl_assert(strcmp(git_buf_cstr(&buf), stat) == 0);
-
-	git_diff_stats_free(stats);
-	git_diff_free(diff);
-	git_commit_free(commit);
+	cl_git_pass(git_diff_stats_to_buf(&buf, _stats, GIT_DIFF_STATS_SHORT, 0));
+	cl_assert_equal_s(stat, git_buf_cstr(&buf));
 	git_buf_free(&buf);
 }
 
 void test_diff_stats__rename(void)
 {
-	git_oid oid;
-	git_commit *commit = NULL;
-	git_diff *diff = NULL;
-	git_diff_stats *stats = NULL;
 	git_buf buf = GIT_BUF_INIT;
-
 	const char *stat =
 	" file2.txt => file2.txt.renamed | 1 +\n"
 	" file3.txt => file3.txt.renamed | 4 +++-\n"
-	" 2 files changed, 4 insertions(+), 1 deletions(-)\n";
-
-	git_oid_fromstr(&oid, "8947a46e2097638ca6040ad4877246f4186ec3bd");
+	" 2 files changed, 4 insertions(+), 1 deletion(-)\n";
 
-	cl_git_pass(git_commit_lookup(&commit, repo, &oid));
-	cl_git_pass(git_diff__commit(&diff, repo, commit, NULL));
-	cl_git_pass(git_diff_find_similar(diff, NULL));
+	diff_stats_from_commit_oid(
+		&_stats, "8947a46e2097638ca6040ad4877246f4186ec3bd", true);
 
-	cl_git_pass(git_diff_get_stats(&stats, diff));
-	cl_assert(git_diff_stats_files_changed(stats) == 2);
-	cl_assert(git_diff_stats_insertions(stats) == 4);
-	cl_assert(git_diff_stats_deletions(stats) == 1);
+	cl_assert_equal_sz(2, git_diff_stats_files_changed(_stats));
+	cl_assert_equal_sz(4, git_diff_stats_insertions(_stats));
+	cl_assert_equal_sz(1, git_diff_stats_deletions(_stats));
 
-	cl_git_pass(git_diff_stats_to_buf(&buf, stats, GIT_DIFF_STATS_FULL));
-	cl_assert(strcmp(git_buf_cstr(&buf), stat) == 0);
-
-	git_diff_stats_free(stats);
-	git_diff_free(diff);
-	git_commit_free(commit);
+	cl_git_pass(git_diff_stats_to_buf(&buf, _stats, GIT_DIFF_STATS_FULL, 0));
+	cl_assert_equal_s(stat, git_buf_cstr(&buf));
 	git_buf_free(&buf);
 }
 
 void test_diff_stats__rename_nochanges(void)
 {
-	git_oid oid;
-	git_commit *commit = NULL;
-	git_diff *diff = NULL;
-	git_diff_stats *stats = NULL;
 	git_buf buf = GIT_BUF_INIT;
-
 	const char *stat =
 	" file2.txt.renamed => file2.txt.renamed2 | 0\n"
 	" file3.txt.renamed => file3.txt.renamed2 | 0\n"
 	" 2 files changed, 0 insertions(+), 0 deletions(-)\n";
 
-	git_oid_fromstr(&oid, "3991dce9e71a0641ca49a6a4eea6c9e7ff402ed4");
-
-	cl_git_pass(git_commit_lookup(&commit, repo, &oid));
-	cl_git_pass(git_diff__commit(&diff, repo, commit, NULL));
-	cl_git_pass(git_diff_find_similar(diff, NULL));
+	diff_stats_from_commit_oid(
+		&_stats, "3991dce9e71a0641ca49a6a4eea6c9e7ff402ed4", true);
 
-	cl_git_pass(git_diff_get_stats(&stats, diff));
-	cl_assert(git_diff_stats_files_changed(stats) == 2);
-	cl_assert(git_diff_stats_insertions(stats) == 0);
-	cl_assert(git_diff_stats_deletions(stats) == 0);
+	cl_assert_equal_sz(2, git_diff_stats_files_changed(_stats));
+	cl_assert_equal_sz(0, git_diff_stats_insertions(_stats));
+	cl_assert_equal_sz(0, git_diff_stats_deletions(_stats));
 
-	cl_git_pass(git_diff_stats_to_buf(&buf, stats, GIT_DIFF_STATS_FULL));
-	cl_assert(strcmp(git_buf_cstr(&buf), stat) == 0);
-
-	git_diff_stats_free(stats);
-	git_diff_free(diff);
-	git_commit_free(commit);
+	cl_git_pass(git_diff_stats_to_buf(&buf, _stats, GIT_DIFF_STATS_FULL, 0));
+	cl_assert_equal_s(stat, git_buf_cstr(&buf));
 	git_buf_free(&buf);
 }
 
 void test_diff_stats__rename_and_modifiy(void)
 {
-	git_oid oid;
-	git_commit *commit = NULL;
-	git_diff *diff = NULL;
-	git_diff_stats *stats = NULL;
 	git_buf buf = GIT_BUF_INIT;
-
 	const char *stat =
 	" file2.txt.renamed2                      | 2 +-\n"
 	" file3.txt.renamed2 => file3.txt.renamed | 0\n"
-	" 2 files changed, 1 insertions(+), 1 deletions(-)\n";
+	" 2 files changed, 1 insertion(+), 1 deletion(-)\n";
 
-	git_oid_fromstr(&oid, "4ca10087e696d2ba78d07b146a118e9a7096ed4f");
+	diff_stats_from_commit_oid(
+		&_stats, "4ca10087e696d2ba78d07b146a118e9a7096ed4f", true);
 
-	cl_git_pass(git_commit_lookup(&commit, repo, &oid));
-	cl_git_pass(git_diff__commit(&diff, repo, commit, NULL));
-	cl_git_pass(git_diff_find_similar(diff, NULL));
+	cl_assert_equal_sz(2, git_diff_stats_files_changed(_stats));
+	cl_assert_equal_sz(1, git_diff_stats_insertions(_stats));
+	cl_assert_equal_sz(1, git_diff_stats_deletions(_stats));
 
-	cl_git_pass(git_diff_get_stats(&stats, diff));
-	cl_assert(git_diff_stats_files_changed(stats) == 2);
-	cl_assert(git_diff_stats_insertions(stats) == 1);
-	cl_assert(git_diff_stats_deletions(stats) == 1);
-
-	cl_git_pass(git_diff_stats_to_buf(&buf, stats, GIT_DIFF_STATS_FULL));
-	cl_assert(strcmp(git_buf_cstr(&buf), stat) == 0);
-
-	git_diff_stats_free(stats);
-	git_diff_free(diff);
-	git_commit_free(commit);
+	cl_git_pass(git_diff_stats_to_buf(&buf, _stats, GIT_DIFF_STATS_FULL, 0));
+	cl_assert_equal_s(stat, git_buf_cstr(&buf));
 	git_buf_free(&buf);
 }
 
 void test_diff_stats__rename_no_find(void)
 {
-	git_oid oid;
-	git_commit *commit = NULL;
-	git_diff *diff = NULL;
-	git_diff_stats *stats = NULL;
 	git_buf buf = GIT_BUF_INIT;
-
 	const char *stat =
 	" file2.txt         | 5 -----\n"
 	" file2.txt.renamed | 6 ++++++\n"
@@ -252,33 +179,21 @@ void test_diff_stats__rename_no_find(void)
 	" file3.txt.renamed | 7 +++++++\n"
 	" 4 files changed, 13 insertions(+), 10 deletions(-)\n";
 
-	git_oid_fromstr(&oid, "8947a46e2097638ca6040ad4877246f4186ec3bd");
+	diff_stats_from_commit_oid(
+		&_stats, "8947a46e2097638ca6040ad4877246f4186ec3bd", false);
 
-	cl_git_pass(git_commit_lookup(&commit, repo, &oid));
-	cl_git_pass(git_diff__commit(&diff, repo, commit, NULL));
+	cl_assert_equal_sz(4, git_diff_stats_files_changed(_stats));
+	cl_assert_equal_sz(13, git_diff_stats_insertions(_stats));
+	cl_assert_equal_sz(10, git_diff_stats_deletions(_stats));
 
-	cl_git_pass(git_diff_get_stats(&stats, diff));
-	cl_assert(git_diff_stats_files_changed(stats) == 4);
-	cl_assert(git_diff_stats_insertions(stats) == 13);
-	cl_assert(git_diff_stats_deletions(stats) == 10);
-
-	cl_git_pass(git_diff_stats_to_buf(&buf, stats, GIT_DIFF_STATS_FULL));
-	cl_assert(strcmp(git_buf_cstr(&buf), stat) == 0);
-
-	git_diff_stats_free(stats);
-	git_diff_free(diff);
-	git_commit_free(commit);
+	cl_git_pass(git_diff_stats_to_buf(&buf, _stats, GIT_DIFF_STATS_FULL, 0));
+	cl_assert_equal_s(stat, git_buf_cstr(&buf));
 	git_buf_free(&buf);
 }
 
 void test_diff_stats__rename_nochanges_no_find(void)
 {
-	git_oid oid;
-	git_commit *commit = NULL;
-	git_diff *diff = NULL;
-	git_diff_stats *stats = NULL;
 	git_buf buf = GIT_BUF_INIT;
-
 	const char *stat =
 	" file2.txt.renamed  | 6 ------\n"
 	" file2.txt.renamed2 | 6 ++++++\n"
@@ -286,143 +201,85 @@ void test_diff_stats__rename_nochanges_no_find(void)
 	" file3.txt.renamed2 | 7 +++++++\n"
 	" 4 files changed, 13 insertions(+), 13 deletions(-)\n";
 
-	git_oid_fromstr(&oid, "3991dce9e71a0641ca49a6a4eea6c9e7ff402ed4");
-
-	cl_git_pass(git_commit_lookup(&commit, repo, &oid));
-	cl_git_pass(git_diff__commit(&diff, repo, commit, NULL));
+	diff_stats_from_commit_oid(
+		&_stats, "3991dce9e71a0641ca49a6a4eea6c9e7ff402ed4", false);
 
-	cl_git_pass(git_diff_get_stats(&stats, diff));
-	cl_assert(git_diff_stats_files_changed(stats) == 4);
-	cl_assert(git_diff_stats_insertions(stats) == 13);
-	cl_assert(git_diff_stats_deletions(stats) == 13);
-
-	cl_git_pass(git_diff_stats_to_buf(&buf, stats, GIT_DIFF_STATS_FULL));
-	cl_assert(strcmp(git_buf_cstr(&buf), stat) == 0);
+	cl_assert_equal_sz(4, git_diff_stats_files_changed(_stats));
+	cl_assert_equal_sz(13, git_diff_stats_insertions(_stats));
+	cl_assert_equal_sz(13, git_diff_stats_deletions(_stats));
 
-	git_diff_stats_free(stats);
-	git_diff_free(diff);
-	git_commit_free(commit);
+	cl_git_pass(git_diff_stats_to_buf(&buf, _stats, GIT_DIFF_STATS_FULL, 0));
+	cl_assert_equal_s(stat, git_buf_cstr(&buf));
 	git_buf_free(&buf);
 }
 
 void test_diff_stats__rename_and_modifiy_no_find(void)
 {
-	git_oid oid;
-	git_commit *commit = NULL;
-	git_diff *diff = NULL;
-	git_diff_stats *stats = NULL;
 	git_buf buf = GIT_BUF_INIT;
-
 	const char *stat =
 	" file2.txt.renamed2 | 2 +-\n"
 	" file3.txt.renamed  | 7 +++++++\n"
 	" file3.txt.renamed2 | 7 -------\n"
 	" 3 files changed, 8 insertions(+), 8 deletions(-)\n";
 
-	git_oid_fromstr(&oid, "4ca10087e696d2ba78d07b146a118e9a7096ed4f");
-
-	cl_git_pass(git_commit_lookup(&commit, repo, &oid));
-	cl_git_pass(git_diff__commit(&diff, repo, commit, NULL));
-
-	cl_git_pass(git_diff_get_stats(&stats, diff));
-	cl_assert(git_diff_stats_files_changed(stats) == 3);
-	cl_assert(git_diff_stats_insertions(stats) == 8);
-	cl_assert(git_diff_stats_deletions(stats) == 8);
+	diff_stats_from_commit_oid(
+		&_stats, "4ca10087e696d2ba78d07b146a118e9a7096ed4f", false);
 
-	cl_git_pass(git_diff_stats_to_buf(&buf, stats, GIT_DIFF_STATS_FULL));
-	cl_assert(strcmp(git_buf_cstr(&buf), stat) == 0);
+	cl_assert_equal_sz(3, git_diff_stats_files_changed(_stats));
+	cl_assert_equal_sz(8, git_diff_stats_insertions(_stats));
+	cl_assert_equal_sz(8, git_diff_stats_deletions(_stats));
 
-	git_diff_stats_free(stats);
-	git_diff_free(diff);
-	git_commit_free(commit);
+	cl_git_pass(git_diff_stats_to_buf(&buf, _stats, GIT_DIFF_STATS_FULL, 0));
+	cl_assert_equal_s(stat, git_buf_cstr(&buf));
 	git_buf_free(&buf);
 }
 
 void test_diff_stats__binary(void)
 {
-	git_oid oid;
-	git_commit *commit = NULL;
-	git_diff *diff = NULL;
-	git_diff_stats *stats = NULL;
 	git_buf buf = GIT_BUF_INIT;
-
-	/* TODO: Actually 0 bytes here should be 5!. Seems like we don't load the new content for binary files? */
 	const char *stat =
 	" binary.bin | Bin 3 -> 0 bytes\n"
 	" 1 file changed, 0 insertions(+), 0 deletions(-)\n";
+	/* TODO: Actually 0 bytes here should be 5!. Seems like we don't load the new content for binary files? */
 
-	git_oid_fromstr(&oid, "8d7523f6fcb2404257889abe0d96f093d9f524f9");
-
-	cl_git_pass(git_commit_lookup(&commit, repo, &oid));
-	cl_git_pass(git_diff__commit(&diff, repo, commit, NULL));
-
-	cl_git_pass(git_diff_get_stats(&stats, diff));
-	cl_assert(git_diff_stats_files_changed(stats) == 1);
-	cl_assert(git_diff_stats_insertions(stats) == 0);
-	cl_assert(git_diff_stats_deletions(stats) == 0);
+	diff_stats_from_commit_oid(
+		&_stats, "8d7523f6fcb2404257889abe0d96f093d9f524f9", false);
 
-	cl_git_pass(git_diff_stats_to_buf(&buf, stats, GIT_DIFF_STATS_FULL));
-	cl_assert(strcmp(git_buf_cstr(&buf), stat) == 0);
+	cl_assert_equal_sz(1, git_diff_stats_files_changed(_stats));
+	cl_assert_equal_sz(0, git_diff_stats_insertions(_stats));
+	cl_assert_equal_sz(0, git_diff_stats_deletions(_stats));
 
-	git_diff_stats_free(stats);
-	git_diff_free(diff);
-	git_commit_free(commit);
+	cl_git_pass(git_diff_stats_to_buf(&buf, _stats, GIT_DIFF_STATS_FULL, 0));
+	cl_assert_equal_s(stat, git_buf_cstr(&buf));
 	git_buf_free(&buf);
 }
 
 void test_diff_stats__binary_numstat(void)
 {
-	git_oid oid;
-	git_commit *commit = NULL;
-	git_diff *diff = NULL;
-	git_diff_stats *stats = NULL;
 	git_buf buf = GIT_BUF_INIT;
-
 	const char *stat =
 	"-       -       binary.bin\n";
 
-	git_oid_fromstr(&oid, "8d7523f6fcb2404257889abe0d96f093d9f524f9");
-
-	cl_git_pass(git_commit_lookup(&commit, repo, &oid));
-	cl_git_pass(git_diff__commit(&diff, repo, commit, NULL));
-
-	cl_git_pass(git_diff_get_stats(&stats, diff));
+	diff_stats_from_commit_oid(
+		&_stats, "8d7523f6fcb2404257889abe0d96f093d9f524f9", false);
 
-	cl_git_pass(git_diff_stats_to_buf(&buf, stats, GIT_DIFF_STATS_NUMBER));
-	cl_assert(strcmp(git_buf_cstr(&buf), stat) == 0);
-
-	git_diff_stats_free(stats);
-	git_diff_free(diff);
-	git_commit_free(commit);
+	cl_git_pass(git_diff_stats_to_buf(&buf, _stats, GIT_DIFF_STATS_NUMBER, 0));
+	cl_assert_equal_s(stat, git_buf_cstr(&buf));
 	git_buf_free(&buf);
 }
 
 void test_diff_stats__mode_change(void)
 {
-	git_oid oid;
-	git_commit *commit = NULL;
-	git_diff *diff = NULL;
-	git_diff_stats *stats = NULL;
 	git_buf buf = GIT_BUF_INIT;
-
 	const char *stat =
 	" file1.txt.renamed | 0\n" \
 	" 1 file changed, 0 insertions(+), 0 deletions(-)\n" \
-	" mode change 100644 => 100755 file1.txt.renamed\n" \
-	"\n";
+		" mode change 100644 => 100755 file1.txt.renamed\n";
 
-	git_oid_fromstr(&oid, "7ade76dd34bba4733cf9878079f9fd4a456a9189");
+	diff_stats_from_commit_oid(
+		&_stats, "7ade76dd34bba4733cf9878079f9fd4a456a9189", false);
 
-	cl_git_pass(git_commit_lookup(&commit, repo, &oid));
-	cl_git_pass(git_diff__commit(&diff, repo, commit, NULL));
-
-	cl_git_pass(git_diff_get_stats(&stats, diff));
-
-	cl_git_pass(git_diff_stats_to_buf(&buf, stats, GIT_DIFF_STATS_FULL | GIT_DIFF_STATS_INCLUDE_SUMMARY));
-	cl_assert(strcmp(git_buf_cstr(&buf), stat) == 0);
-
-	git_diff_stats_free(stats);
-	git_diff_free(diff);
-	git_commit_free(commit);
+	cl_git_pass(git_diff_stats_to_buf(&buf, _stats, GIT_DIFF_STATS_FULL | GIT_DIFF_STATS_INCLUDE_SUMMARY, 0));
+	cl_assert_equal_s(stat, git_buf_cstr(&buf));
 	git_buf_free(&buf);
 }