str: introduce `git_str` for internal, `git_buf` is externalethomson/gitstr

libgit2 has two distinct requirements that were previously solved by
`git_buf`.  We require:

1. A general purpose string class that provides a number of utility APIs
   for manipulating data (eg, concatenating, truncating, etc).
2. A structure that we can use to return strings to callers that they
   can take ownership of.

By using a single class (`git_buf`) for both of these purposes, we have
confused the API to the point that refactorings are difficult and
reasoning about correctness is also difficult.

Move the utility class `git_buf` to be called `git_str`: this represents
its general purpose, as an internal string buffer class.  The name also
is an homage to Junio Hamano ("gitstr").

The public API remains `git_buf`, and has a much smaller footprint.  It
is generally only used as an "out" param with strict requirements that
follow the documentation.  (Exceptions exist for some legacy APIs to
avoid breaking callers unnecessarily.)

Utility functions exist to convert a user-specified `git_buf` to a
`git_str` so that we can call internal functions, then converting it
back again.

1 files changed, 39 insertions, 28 deletions

diff --git a/src/diff_stats.c b/src/diff_stats.c
index 41a25bf8a..228f6f892 100644
--- a/src/diff_stats.c
+++ b/src/diff_stats.c
@@ -5,8 +5,10 @@
  * a Linking Exception. For full terms see the included COPYING file.
  */
 
-#include "common.h"
+#include "diff_stats.h"
 
+#include "buf.h"
+#include "common.h"
 #include "vector.h"
 #include "diff.h"
 #include "patch_generate.h"
@@ -47,7 +49,7 @@ static int digits_for_value(size_t val)
 }
 
 static int diff_file_stats_full_to_buf(
-	git_buf *out,
+	git_str *out,
 	const git_diff_delta *delta,
 	const diff_file_stats *filestat,
 	const git_diff_stats *stats,
@@ -70,12 +72,12 @@ static int diff_file_stats_full_to_buf(
 
 		if ((common_dirlen = git_path_common_dirlen(old_path, new_path)) &&
 		    common_dirlen <= INT_MAX) {
-			error = git_buf_printf(out, " %.*s{%s"DIFF_RENAME_FILE_SEPARATOR"%s}",
+			error = git_str_printf(out, " %.*s{%s"DIFF_RENAME_FILE_SEPARATOR"%s}",
 					       (int) common_dirlen, old_path,
 					       old_path + common_dirlen,
 					       new_path + common_dirlen);
 		} else {
-			error = git_buf_printf(out, " %s" DIFF_RENAME_FILE_SEPARATOR "%s",
+			error = git_str_printf(out, " %s" DIFF_RENAME_FILE_SEPARATOR "%s",
 					       old_path, new_path);
 		}
 
@@ -83,7 +85,7 @@ static int diff_file_stats_full_to_buf(
 			goto on_error;
 	} else {
 		adddel_path = new_path ? new_path : old_path;
-		if (git_buf_printf(out, " %s", adddel_path) < 0)
+		if (git_str_printf(out, " %s", adddel_path) < 0)
 			goto on_error;
 
 		padding = stats->max_name - strlen(adddel_path);
@@ -92,28 +94,28 @@ static int diff_file_stats_full_to_buf(
 			padding += strlen(DIFF_RENAME_FILE_SEPARATOR);
 	}
 
-	if (git_buf_putcn(out, ' ', padding) < 0 ||
-		git_buf_puts(out, " | ") < 0)
+	if (git_str_putcn(out, ' ', padding) < 0 ||
+		git_str_puts(out, " | ") < 0)
 		goto on_error;
 
 	if (delta->flags & GIT_DIFF_FLAG_BINARY) {
-		if (git_buf_printf(out,
+		if (git_str_printf(out,
 				"Bin %" PRId64 " -> %" PRId64 " bytes", old_size, new_size) < 0)
 			goto on_error;
 	}
 	else {
-		if (git_buf_printf(out,
+		if (git_str_printf(out,
 				"%*" PRIuZ, stats->max_digits,
 				filestat->insertions + filestat->deletions) < 0)
 			goto on_error;
 
 		if (filestat->insertions || filestat->deletions) {
-			if (git_buf_putc(out, ' ') < 0)
+			if (git_str_putc(out, ' ') < 0)
 				goto on_error;
 
 			if (!width) {
-				if (git_buf_putcn(out, '+', filestat->insertions) < 0 ||
-					git_buf_putcn(out, '-', filestat->deletions) < 0)
+				if (git_str_putcn(out, '+', filestat->insertions) < 0 ||
+					git_str_putcn(out, '-', filestat->deletions) < 0)
 					goto on_error;
 			} else {
 				size_t total = filestat->insertions + filestat->deletions;
@@ -122,21 +124,21 @@ static int diff_file_stats_full_to_buf(
 				size_t plus = full * filestat->insertions / total;
 				size_t minus = full - plus;
 
-				if (git_buf_putcn(out, '+', max(plus,  1)) < 0 ||
-					git_buf_putcn(out, '-', max(minus, 1)) < 0)
+				if (git_str_putcn(out, '+', max(plus,  1)) < 0 ||
+					git_str_putcn(out, '-', max(minus, 1)) < 0)
 					goto on_error;
 			}
 		}
 	}
 
-	git_buf_putc(out, '\n');
+	git_str_putc(out, '\n');
 
 on_error:
-	return (git_buf_oom(out) ? -1 : 0);
+	return (git_str_oom(out) ? -1 : 0);
 }
 
 static int diff_file_stats_number_to_buf(
-	git_buf *out,
+	git_str *out,
 	const git_diff_delta *delta,
 	const diff_file_stats *filestats)
 {
@@ -144,29 +146,29 @@ static int diff_file_stats_number_to_buf(
 	const char *path = delta->new_file.path;
 
 	if (delta->flags & GIT_DIFF_FLAG_BINARY)
-		error = git_buf_printf(out, "%-8c" "%-8c" "%s\n", '-', '-', path);
+		error = git_str_printf(out, "%-8c" "%-8c" "%s\n", '-', '-', path);
 	else
-		error = git_buf_printf(out, "%-8" PRIuZ "%-8" PRIuZ "%s\n",
+		error = git_str_printf(out, "%-8" PRIuZ "%-8" PRIuZ "%s\n",
 			filestats->insertions, filestats->deletions, path);
 
 	return error;
 }
 
 static int diff_file_stats_summary_to_buf(
-	git_buf *out,
+	git_str *out,
 	const git_diff_delta *delta)
 {
 	if (delta->old_file.mode != delta->new_file.mode) {
 		if (delta->old_file.mode == 0) {
-			git_buf_printf(out, " create mode %06o %s\n",
+			git_str_printf(out, " create mode %06o %s\n",
 				delta->new_file.mode, delta->new_file.path);
 		}
 		else if (delta->new_file.mode == 0) {
-			git_buf_printf(out, " delete mode %06o %s\n",
+			git_str_printf(out, " delete mode %06o %s\n",
 				delta->old_file.mode, delta->old_file.path);
 		}
 		else {
-			git_buf_printf(out, " mode change %06o => %06o %s\n",
+			git_str_printf(out, " mode change %06o => %06o %s\n",
 				delta->old_file.mode, delta->new_file.mode, delta->new_file.path);
 		}
 	}
@@ -279,6 +281,15 @@ int git_diff_stats_to_buf(
 	git_diff_stats_format_t format,
 	size_t width)
 {
+	GIT_BUF_WRAP_PRIVATE(out, git_diff__stats_to_buf, stats, format, width);
+}
+
+int git_diff__stats_to_buf(
+	git_str *out,
+	const git_diff_stats *stats,
+	git_diff_stats_format_t format,
+	size_t width)
+{
 	int error = 0;
 	size_t i;
 	const git_diff_delta *delta;
@@ -320,23 +331,23 @@ int git_diff_stats_to_buf(
 	}
 
 	if (format & GIT_DIFF_STATS_FULL || format & GIT_DIFF_STATS_SHORT) {
-		git_buf_printf(
+		git_str_printf(
 			out, " %" PRIuZ " file%s changed",
 			stats->files_changed, stats->files_changed != 1 ? "s" : "");
 
 		if (stats->insertions || stats->deletions == 0)
-			git_buf_printf(
+			git_str_printf(
 				out, ", %" PRIuZ " insertion%s(+)",
 				stats->insertions, stats->insertions != 1 ? "s" : "");
 
 		if (stats->deletions || stats->insertions == 0)
-			git_buf_printf(
+			git_str_printf(
 				out, ", %" PRIuZ " deletion%s(-)",
 				stats->deletions, stats->deletions != 1 ? "s" : "");
 
-		git_buf_putc(out, '\n');
+		git_str_putc(out, '\n');
 
-		if (git_buf_oom(out))
+		if (git_str_oom(out))
 			return -1;
 	}