Extend git_buf with new utility functions and unit tests.

Add new functions to git_buf for:
* initializing a buffer from a string
* joining one or more strings onto a buffer with separators
* swapping two buffers in place
* extracting data from a git_buf (leaving it empty)

Also, make git_buf_free leave a git_buf back in its initted state,
and slightly tweak buffer allocation sizes and thresholds.

Finally, port unit tests to clay and extend with lots of new tests
for the various git_buf functions.

src/buffer.c

@@ -9,7 +9,7 @@
 #include <stdarg.h>
 
 #define ENSURE_SIZE(b, d) \
-	if ((ssize_t)(d) >= buf->asize && git_buf_grow(b, (d)) < GIT_SUCCESS)\
+	if ((ssize_t)(d) > buf->asize && git_buf_grow(b, (d)) < GIT_SUCCESS)\
 		return;
 
 int git_buf_grow(git_buf *buf, size_t target_size)
@@ -19,6 +19,9 @@ int git_buf_grow(git_buf *buf, size_t target_size)
 	if (buf->asize < 0)
 		return GIT_ENOMEM;
 
+	if (target_size <= (size_t)buf->asize)
+		return GIT_SUCCESS;
+
 	if (buf->asize == 0)
 		buf->asize = target_size;
 
@@ -27,6 +30,9 @@ int git_buf_grow(git_buf *buf, size_t target_size)
 	while (buf->asize < (int)target_size)
 		buf->asize = (buf->asize << 1) - (buf->asize >> 1);
 
+	/* round allocation up to multiple of 8 */
+	buf->asize = (buf->asize + 7) & ~7;
+
 	new_ptr = git__realloc(buf->ptr, buf->asize);
 	if (!new_ptr) {
 		buf->asize = -1;
@@ -42,6 +48,22 @@ int git_buf_oom(const git_buf *buf)
 	return (buf->asize < 0);
 }
 
+void git_buf_set(git_buf *buf, const char *data, size_t len)
+{
+	if (len == 0 || data == NULL) {
+		git_buf_clear(buf);
+	} else {
+		ENSURE_SIZE(buf, len);
+		memmove(buf->ptr, data, len);
+		buf->size = len;
+	}
+}
+
+void git_buf_sets(git_buf *buf, const char *string)
+{
+	git_buf_set(buf, string, string ? strlen(string) : 0);
+}
+
 void git_buf_putc(git_buf *buf, char c)
 {
 	ENSURE_SIZE(buf, buf->size + 1);
@@ -51,13 +73,14 @@ void git_buf_putc(git_buf *buf, char c)
 void git_buf_put(git_buf *buf, const char *data, size_t len)
 {
 	ENSURE_SIZE(buf, buf->size + len);
-	memcpy(buf->ptr + buf->size, data, len);
+	memmove(buf->ptr + buf->size, data, len);
 	buf->size += len;
 }
 
 void git_buf_puts(git_buf *buf, const char *string)
 {
-	git_buf_put(buf, string, strlen(string));
+	if (string != NULL)
+		git_buf_put(buf, string, strlen(string));
 }
 
 void git_buf_printf(git_buf *buf, const char *format, ...)
@@ -88,7 +111,8 @@ void git_buf_printf(git_buf *buf, const char *format, ...)
 
 const char *git_buf_cstr(git_buf *buf)
 {
-	if (buf->size + 1 >= buf->asize && git_buf_grow(buf, buf->size + 1) < GIT_SUCCESS)
+	if (buf->size + 1 > buf->asize &&
+		git_buf_grow(buf, buf->size + 1) < GIT_SUCCESS)
 		return NULL;
 
 	buf->ptr[buf->size] = '\0';
@@ -97,7 +121,14 @@ const char *git_buf_cstr(git_buf *buf)
 
 void git_buf_free(git_buf *buf)
 {
-	git__free(buf->ptr);
+	if (buf) {
+		if (buf->ptr) {
+			git__free(buf->ptr);
+			buf->ptr = NULL;
+		}
+		buf->asize = 0;
+		buf->size = 0;
+	}
 }
 
 void git_buf_clear(git_buf *buf)
@@ -107,7 +138,104 @@ void git_buf_clear(git_buf *buf)
 
 void git_buf_consume(git_buf *buf, const char *end)
 {
-	size_t consumed = end - buf->ptr;
-	memmove(buf->ptr, end, buf->size - consumed);
-	buf->size -= consumed;
+	if (end > buf->ptr && end <= buf->ptr + buf->size) {
+		size_t consumed = end - buf->ptr;
+		memmove(buf->ptr, end, buf->size - consumed);
+		buf->size -= consumed;
+	}
+}
+
+void git_buf_swap(git_buf *buf_a, git_buf *buf_b)
+{
+	git_buf t = *buf_a;
+	*buf_a = *buf_b;
+	*buf_b = t;
 }
+
+char *git_buf_take_cstr(git_buf *buf)
+{
+	char *data = NULL;
+
+	if (buf->ptr == NULL)
+		return NULL;
+
+	if (buf->size + 1 > buf->asize &&
+		git_buf_grow(buf, buf->size + 1) < GIT_SUCCESS)
+		return NULL;
+
+	data = buf->ptr;
+	data[buf->size] = '\0';
+
+	buf->ptr = NULL;
+	buf->asize = 0;
+	buf->size = 0;
+
+	return data;
+}
+
+void git_buf_join(git_buf *buf, char separator, int nbuf, ...)
+{
+	/* Make two passes to avoid multiple reallocation */
+
+	va_list ap;
+	int i;
+	int total_size = 0;
+	char *out;
+
+	if (buf->size > 0 && buf->ptr[buf->size - 1] != separator)
+		++total_size; /* space for initial separator */
+
+	va_start(ap, nbuf);
+	for (i = 0; i < nbuf; ++i) {
+		const char* segment;
+		int segment_len;
+
+		segment = va_arg(ap, const char *);
+		if (!segment)
+			continue;
+
+		segment_len = strlen(segment);
+		total_size += segment_len;
+		if (segment_len == 0 || segment[segment_len - 1] != separator)
+			++total_size; /* space for separator */
+	}
+	va_end(ap);
+
+	ENSURE_SIZE(buf, buf->size + total_size);
+
+	out = buf->ptr + buf->size;
+
+	/* append separator to existing buf if needed */
+	if (buf->size > 0 && out[-1] != separator)
+		*out++ = separator;
+
+	va_start(ap, nbuf);
+	for (i = 0; i < nbuf; ++i) {
+		const char* segment;
+		int segment_len;
+
+		segment = va_arg(ap, const char *);
+		if (!segment)
+			continue;
+
+		/* skip leading separators */
+		if (out > buf->ptr && out[-1] == separator)
+			while (*segment == separator) segment++;
+
+		/* copy over next buffer */
+		segment_len = strlen(segment);
+		if (segment_len > 0) {
+			memmove(out, segment, segment_len);
+			out += segment_len;
+		}
+
+		/* append trailing separator (except for last item) */
+		if (i < nbuf - 1 && out > buf->ptr && out[-1] != separator)
+			*out++ = separator;
+	}
+	va_end(ap);
+
+	/* set size based on num characters actually written */
+	buf->size = out - buf->ptr;
+}
+

src/buffer.h

@@ -17,15 +17,30 @@ typedef struct {
 #define GIT_BUF_INIT {NULL, 0, 0}
 
 int git_buf_grow(git_buf *buf, size_t target_size);
+void git_buf_free(git_buf *buf);
+void git_buf_swap(git_buf *buf_a, git_buf *buf_b);
+
+/**
+ * Any function that writes to a git_buf can fail due to memory allocation
+ * issues.  If one fails, the git_buf will be marked with an OOM error and
+ * further calls to modify the buffer will fail.  You just check
+ * git_buf_oom() at the end of your sequence and it will be true if you ran
+ * out of memory at any point with that buffer.
+ */
 int git_buf_oom(const git_buf *buf);
+
+void git_buf_set(git_buf *buf, const char *data, size_t len);
+void git_buf_sets(git_buf *buf, const char *string);
 void git_buf_putc(git_buf *buf, char c);
 void git_buf_put(git_buf *buf, const char *data, size_t len);
 void git_buf_puts(git_buf *buf, const char *string);
 void git_buf_printf(git_buf *buf, const char *format, ...) GIT_FORMAT_PRINTF(2, 3);
-const char *git_buf_cstr(git_buf *buf);
-void git_buf_free(git_buf *buf);
 void git_buf_clear(git_buf *buf);
 void git_buf_consume(git_buf *buf, const char *end);
+void git_buf_join(git_buf *buf, char separator, int nbuf, ...);
+
+const char *git_buf_cstr(git_buf *buf);
+char *git_buf_take_cstr(git_buf *buf);
 
 #define git_buf_PUTS(buf, str) git_buf_put(buf, str, sizeof(str) - 1)
 

tests-clay/clay_libgit2.h

@@ -25,4 +25,20 @@
  */
 #define cl_git_fail(expr) cl_must_fail(expr)
 
+/**
+ * Wrapper for string comparison that knows about nulls.
+ */
+#define cl_assert_strequal(a,b) \
+	cl_assert_strequal_internal(a,b,__FILE__,__LINE__)
+
+GIT_INLINE(void) cl_assert_strequal_internal(const char *a, const char *b, const char *file, int line)
+{
+	int match = (a == NULL || b == NULL) ? (a == b) : (strcmp(a, b) == 0);
+	if (!match) {
+		char buf[4096];
+		snprintf(buf, 4096, "'%s' != '%s'", a, b);
+		clay__assert(0, file, line, buf, "Strings do not match", 1);
+	}
+}
+
 #endif

tests-clay/core/buffer.c

+#include "clay_libgit2.h"
+#include "buffer.h"
+
+#define TESTSTR "Have you seen that? Have you seeeen that??"
+const char *test_string = TESTSTR;
+const char *test_string_x2 = TESTSTR TESTSTR;
+
+#define REP4(STR)	 STR STR STR STR
+#define REP16(STR)	 REP4(REP4(STR))
+#define REP1024(STR) REP16(REP16(REP4(STR)))
+#define TESTSTR_4096 REP1024("1234")
+#define TESTSTR_8192 REP1024("12341234")
+const char *test_4096 = TESTSTR_4096;
+const char *test_8192 = TESTSTR_8192;
+
+/* test basic data concatenation */
+void test_core_buffer__0(void)
+{
+	git_buf buf = GIT_BUF_INIT;
+
+	cl_assert(buf.size == 0);
+
+	git_buf_puts(&buf, test_string);
+	cl_assert(git_buf_oom(&buf) == 0);
+	cl_assert_strequal(test_string, git_buf_cstr(&buf));
+
+	git_buf_puts(&buf, test_string);
+	cl_assert(git_buf_oom(&buf) == 0);
+	cl_assert_strequal(test_string_x2, git_buf_cstr(&buf));
+
+	git_buf_free(&buf);
+}
+
+/* test git_buf_printf */
+void test_core_buffer__1(void)
+{
+	git_buf buf = GIT_BUF_INIT;
+
+	git_buf_printf(&buf, "%s %s %d ", "shoop", "da", 23);
+	cl_assert(git_buf_oom(&buf) == 0);
+	cl_assert_strequal("shoop da 23 ", git_buf_cstr(&buf));
+
+	git_buf_printf(&buf, "%s %d", "woop", 42);
+	cl_assert(git_buf_oom(&buf) == 0);
+	cl_assert_strequal("shoop da 23 woop 42", git_buf_cstr(&buf));
+
+	git_buf_free(&buf);
+}
+
+/* more thorough test of concatenation options */
+void test_core_buffer__2(void)
+{
+	git_buf buf = GIT_BUF_INIT;
+	int i;
+
+	cl_assert(buf.size == 0);
+
+	/* this must be safe to do */
+	git_buf_free(&buf);
+
+	cl_assert(buf.size == 0);
+	cl_assert(buf.asize == 0);
+
+	/* empty buffer should be empty string */
+	cl_assert_strequal("", git_buf_cstr(&buf));
+	cl_assert(buf.size == 0);
+	cl_assert(buf.asize > 0);
+
+	/* free should set us back to the beginning */
+	git_buf_free(&buf);
+	cl_assert(buf.size == 0);
+	cl_assert(buf.asize == 0);
+
+	/* add letter */
+	git_buf_putc(&buf, '+');
+	cl_assert(git_buf_oom(&buf) == 0);
+	cl_assert_strequal("+", git_buf_cstr(&buf));
+
+	/* add letter again */
+	git_buf_putc(&buf, '+');
+	cl_assert(git_buf_oom(&buf) == 0);
+	cl_assert_strequal("++", git_buf_cstr(&buf));
+
+	/* let's try that a few times */
+	for (i = 0; i < 16; ++i) {
+		git_buf_putc(&buf, '+');
+		cl_assert(git_buf_oom(&buf) == 0);
+	}
+	cl_assert_strequal("++++++++++++++++++", git_buf_cstr(&buf));
+
+	git_buf_free(&buf);
+
+	/* add data */
+	git_buf_put(&buf, "xo", 2);
+	cl_assert(git_buf_oom(&buf) == 0);
+	cl_assert_strequal("xo", git_buf_cstr(&buf));
+
+	/* add letter again */
+	git_buf_put(&buf, "xo", 2);
+	cl_assert(git_buf_oom(&buf) == 0);
+	cl_assert_strequal("xoxo", git_buf_cstr(&buf));
+
+	/* let's try that a few times */
+	for (i = 0; i < 16; ++i) {
+		git_buf_put(&buf, "xo", 2);
+		cl_assert(git_buf_oom(&buf) == 0);
+	}
+	cl_assert_strequal("xoxoxoxoxoxoxoxoxoxoxoxoxoxoxoxoxoxo",
+					   git_buf_cstr(&buf));
+
+	git_buf_free(&buf);
+
+	/* set to string */
+	git_buf_sets(&buf, test_string);
+	cl_assert(git_buf_oom(&buf) == 0);
+	cl_assert_strequal(test_string, git_buf_cstr(&buf));
+
+	/* append string */
+	git_buf_puts(&buf, test_string);
+	cl_assert(git_buf_oom(&buf) == 0);
+	cl_assert_strequal(test_string_x2, git_buf_cstr(&buf));
+
+	/* set to string again (should overwrite - not append) */
+	git_buf_sets(&buf, test_string);
+	cl_assert(git_buf_oom(&buf) == 0);
+	cl_assert_strequal(test_string, git_buf_cstr(&buf));
+
+	/* test clear */
+	git_buf_clear(&buf);
+	cl_assert_strequal("", git_buf_cstr(&buf));
+
+	git_buf_free(&buf);
+}
+
+/* let's do some tests with larger buffers to push our limits */
+void test_core_buffer__3(void)
+{
+	git_buf buf = GIT_BUF_INIT;
+
+	/* set to string */
+	git_buf_set(&buf, test_4096, 4096);
+	cl_assert(git_buf_oom(&buf) == 0);
+	cl_assert_strequal(test_4096, git_buf_cstr(&buf));
+
+	/* append string */
+	git_buf_puts(&buf, test_4096);
+	cl_assert(git_buf_oom(&buf) == 0);
+	cl_assert_strequal(test_8192, git_buf_cstr(&buf));
+
+	/* set to string again (should overwrite - not append) */
+	git_buf_set(&buf, test_4096, 4096);
+	cl_assert(git_buf_oom(&buf) == 0);
+	cl_assert_strequal(test_4096, git_buf_cstr(&buf));
+
+	git_buf_free(&buf);
+}
+
+/* let's try some producer/consumer tests */
+void test_core_buffer__4(void)
+{
+	git_buf buf = GIT_BUF_INIT;
+	int i;
+
+	for (i = 0; i < 10; ++i) {
+		git_buf_puts(&buf, "1234"); /* add 4 */
+		cl_assert(git_buf_oom(&buf) == 0);
+		git_buf_consume(&buf, buf.ptr + 2); /* eat the first two */
+		cl_assert(strlen(git_buf_cstr(&buf)) == (size_t)((i + 1) * 2));
+	}
+	/* we have appended 1234 10x and removed the first 20 letters */
+	cl_assert_strequal("12341234123412341234", git_buf_cstr(&buf));
+
+	git_buf_consume(&buf, NULL);
+	cl_assert_strequal("12341234123412341234", git_buf_cstr(&buf));
+
+	git_buf_consume(&buf, "invalid pointer");
+	cl_assert_strequal("12341234123412341234", git_buf_cstr(&buf));
+
+	git_buf_consume(&buf, buf.ptr);
+	cl_assert_strequal("12341234123412341234", git_buf_cstr(&buf));
+
+	git_buf_consume(&buf, buf.ptr + 1);
+	cl_assert_strequal("2341234123412341234", git_buf_cstr(&buf));
+
+	git_buf_consume(&buf, buf.ptr + buf.size);
+	cl_assert_strequal("", git_buf_cstr(&buf));
+
+	git_buf_free(&buf);
+}
+
+
+static void
+check_buf_append(
+	const char* data_a,
+	const char* data_b,
+	const char* expected_data,
+	ssize_t expected_size,
+	ssize_t expected_asize)
+{
+	git_buf tgt = GIT_BUF_INIT;
+
+	git_buf_sets(&tgt, data_a);
+	cl_assert(git_buf_oom(&tgt) == 0);
+	git_buf_puts(&tgt, data_b);
+	cl_assert(git_buf_oom(&tgt) == 0);
+	if (expected_data == NULL)
+		cl_assert(tgt.ptr == NULL);
+	else
+		cl_assert_strequal(expected_data, git_buf_cstr(&tgt));
+	cl_assert(tgt.size == expected_size);
+	if (expected_asize > 0)
+		cl_assert(tgt.asize == expected_asize);
+
+	git_buf_free(&tgt);
+}
+
+static void
+check_buf_append_abc(
+	const char* buf_a,
+	const char* buf_b,
+	const char* buf_c,
+	const char* expected_ab,
+	const char* expected_abc,
+	const char* expected_abca,
+	const char* expected_abcab,
+	const char* expected_abcabc)
+{
+	git_buf buf = GIT_BUF_INIT;
+
+	git_buf_sets(&buf, buf_a);
+	cl_assert(git_buf_oom(&buf) == 0);
+	cl_assert_strequal(buf_a, git_buf_cstr(&buf));
+
+	git_buf_puts(&buf, buf_b);
+	cl_assert(git_buf_oom(&buf) == 0);
+	cl_assert_strequal(expected_ab, git_buf_cstr(&buf));
+
+	git_buf_puts(&buf, buf_c);
+	cl_assert(git_buf_oom(&buf) == 0);
+	cl_assert_strequal(expected_abc, git_buf_cstr(&buf));
+
+	git_buf_puts(&buf, buf_a);
+	cl_assert(git_buf_oom(&buf) == 0);
+	cl_assert_strequal(expected_abca, git_buf_cstr(&buf));
+
+	git_buf_puts(&buf, buf_b);
+	cl_assert(git_buf_oom(&buf) == 0);
+	cl_assert_strequal(expected_abcab, git_buf_cstr(&buf));
+
+	git_buf_puts(&buf, buf_c);
+	cl_assert(git_buf_oom(&buf) == 0);
+	cl_assert_strequal(expected_abcabc, git_buf_cstr(&buf));
+
+	git_buf_free(&buf);
+}
+
+/* more variations on append tests */
+void test_core_buffer__5(void)
+{
+	check_buf_append(NULL, NULL, NULL, 0, 0);
+	check_buf_append(NULL, "", "", 0, 8);
+	check_buf_append("", NULL, "", 0, 8);
+	check_buf_append("", "", "", 0, 8);
+	check_buf_append("a", NULL, "a", 1, 8);
+	check_buf_append(NULL, "a", "a", 1, 8);
+	check_buf_append("", "a", "a", 1, 8);
+	check_buf_append("a", "", "a", 1, 8);
+	check_buf_append("a", "b", "ab", 2, 8);
+	check_buf_append("", "abcdefgh", "abcdefgh", 8, 16);
+	check_buf_append("abcdefgh", "", "abcdefgh", 8, 16);
+
+	/* buffer with starting asize will grow to:
+	 *  1 ->  2,  2 ->  3,  3 ->  5,  4 ->  6,  5 ->  8,  6 ->  9,
+	 *  7 -> 11,  8 -> 12,  9 -> 14, 10 -> 15, 11 -> 17, 12 -> 18,
+	 * 13 -> 20, 14 -> 21, 15 -> 23, 16 -> 24, 17 -> 26, 18 -> 27,
+	 * 19 -> 29, 20 -> 30, 21 -> 32, 22 -> 33, 23 -> 35, 24 -> 36,
+	 * ...
+	 * follow sequence until value > target size,
+	 * then round up to nearest multiple of 8.
+	 */
+
+	check_buf_append("abcdefgh", "/", "abcdefgh/", 9, 16);
+	check_buf_append("abcdefgh", "ijklmno", "abcdefghijklmno", 15, 24);
+	check_buf_append("abcdefgh", "ijklmnop", "abcdefghijklmnop", 16, 24);
+	check_buf_append("0123456789", "0123456789",
+					 "01234567890123456789", 20, 24);
+	check_buf_append(REP16("x"), REP16("o"),
+					 REP16("x") REP16("o"), 32, 40);
+
+	check_buf_append(test_4096, NULL, test_4096, 4096, 6144);
+	check_buf_append(test_4096, "", test_4096, 4096, 6144);
+	check_buf_append(test_4096, test_4096, test_8192, 8192, 9216);
+
+	/* check sequences of appends */
+	check_buf_append_abc("a", "b", "c",
+						 "ab", "abc", "abca", "abcab", "abcabc");
+	check_buf_append_abc("a1", "b2", "c3",
+						 "a1b2", "a1b2c3", "a1b2c3a1",
+						 "a1b2c3a1b2", "a1b2c3a1b2c3");
+	check_buf_append_abc("a1/", "b2/", "c3/",
+						 "a1/b2/", "a1/b2/c3/", "a1/b2/c3/a1/",
+						 "a1/b2/c3/a1/b2/", "a1/b2/c3/a1/b2/c3/");
+}
+
+/* test swap */
+void test_core_buffer__6(void)
+{
+	git_buf a = GIT_BUF_INIT;
+	git_buf b = GIT_BUF_INIT;
+
+	git_buf_sets(&a, "foo");
+	cl_assert(git_buf_oom(&a) == 0);
+	git_buf_sets(&b, "bar");
+	cl_assert(git_buf_oom(&b) == 0);
+
+	cl_assert_strequal("foo", git_buf_cstr(&a));
+	cl_assert_strequal("bar", git_buf_cstr(&b));
+
+	git_buf_swap(&a, &b);
+
+	cl_assert_strequal("bar", git_buf_cstr(&a));
+	cl_assert_strequal("foo", git_buf_cstr(&b));
+
+	git_buf_free(&a);
+	git_buf_free(&b);
+}
+
+
+/* test take cstr data */
+void test_core_buffer__7(void)
+{
+	git_buf a = GIT_BUF_INIT;
+	char *b = NULL;
+
+	git_buf_sets(&a, "foo");
+	cl_assert(git_buf_oom(&a) == 0);
+	cl_assert_strequal("foo", git_buf_cstr(&a));
+
+	b = git_buf_take_cstr(&a);
+
+	cl_assert_strequal("foo", b);
+	cl_assert_strequal(NULL, a.ptr);
+	git__free(b);
+
+	b = git_buf_take_cstr(&a);
+
+	cl_assert_strequal(NULL, b);
+	cl_assert_strequal(NULL, a.ptr);
+
+	git_buf_free(&a);
+}
+
+
+static void
+check_joinbuf(
+	const char *a,
+	const char *b,
+	const char *expected)
+{
+	char sep = '/';
+	git_buf buf = GIT_BUF_INIT;
+
+	git_buf_sets(&buf, a);
+	cl_assert(git_buf_oom(&buf) == 0);
+
+	git_buf_join(&buf, sep, 1, b);
+	cl_assert(git_buf_oom(&buf) == 0);
+	cl_assert_strequal(expected, git_buf_cstr(&buf));
+
+	git_buf_free(&buf);
+}
+
+static void
+check_joinbuf_n(
+	const char *a,
+	const char *b,
+	const char *c,
+	const char *d,
+	const char *expected)
+{
+	char sep = ';';
+	git_buf buf = GIT_BUF_INIT;
+	git_buf_join(&buf, sep, 4, a, b, c, d);
+	cl_assert(git_buf_oom(&buf) == 0);
+	cl_assert_strequal(expected, git_buf_cstr(&buf));
+	git_buf_free(&buf);
+}
+
+/* test join */
+void test_core_buffer__8(void)
+{
+	git_buf a = GIT_BUF_INIT;
+
+	git_buf_join(&a, '/', 1, "foo");
+	cl_assert(git_buf_oom(&a) == 0);
+	cl_assert_strequal("foo", git_buf_cstr(&a));
+
+	git_buf_join(&a, '/', 1, "bar");
+	cl_assert(git_buf_oom(&a) == 0);
+	cl_assert_strequal("foo/bar", git_buf_cstr(&a));
+
+	git_buf_join(&a, '/', 1, "baz");
+	cl_assert(git_buf_oom(&a) == 0);
+	cl_assert_strequal("foo/bar/baz", git_buf_cstr(&a));
+
+	git_buf_free(&a);
+
+	check_joinbuf("", "", "");
+	check_joinbuf("", "a", "a");
+	check_joinbuf("", "/a", "/a");
+	check_joinbuf("a", "", "a/");
+	check_joinbuf("a", "/", "a/");
+	check_joinbuf("a", "b", "a/b");
+	check_joinbuf("/", "a", "/a");
+	check_joinbuf("/", "", "/");
+	check_joinbuf("/a", "/b", "/a/b");
+	check_joinbuf("/a", "/b/", "/a/b/");
+	check_joinbuf("/a/", "b/", "/a/b/");
+	check_joinbuf("/a/", "/b/", "/a/b/");
+	check_joinbuf("/abcd", "/defg", "/abcd/defg");
+	check_joinbuf("/abcd", "/defg/", "/abcd/defg/");
+	check_joinbuf("/abcd/", "defg/", "/abcd/defg/");
+	check_joinbuf("/abcd/", "/defg/", "/abcd/defg/");
+
+	check_joinbuf_n("", "", "", "", "");
+	check_joinbuf_n("", "a", "", "", "a;");
+	check_joinbuf_n("a", "", "", "", "a;");
+	check_joinbuf_n("", "", "", "a", "a");
+	check_joinbuf_n("a", "b", "", ";c;d;", "a;b;c;d;");
+	check_joinbuf_n("a", "b", "", ";c;d", "a;b;c;d");
+	check_joinbuf_n("abcd", "efgh", "ijkl", "mnop", "abcd;efgh;ijkl;mnop");
+	check_joinbuf_n("abcd;", "efgh;", "ijkl;", "mnop;", "abcd;efgh;ijkl;mnop;");
+	check_joinbuf_n(";abcd;", ";efgh;", ";ijkl;", ";mnop;", ";abcd;efgh;ijkl;mnop;");
+}
+