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.

4 files changed, 22 insertions, 23 deletions

diff --git a/fuzzers/commit_graph_fuzzer.c b/fuzzers/commit_graph_fuzzer.c
index 39b520882..05783a259 100644
--- a/fuzzers/commit_graph_fuzzer.c
+++ b/fuzzers/commit_graph_fuzzer.c
@@ -11,8 +11,8 @@
 
 #include "git2.h"
 
-#include "buffer.h"
 #include "common.h"
+#include "str.h"
 #include "futils.h"
 #include "hash.h"
 #include "commit_graph.h"
@@ -33,7 +33,7 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
 {
 	git_commit_graph_file file = {{0}};
 	git_commit_graph_entry e;
-	git_buf commit_graph_buf = GIT_BUF_INIT;
+	git_str commit_graph_buf = GIT_STR_INIT;
 	unsigned char hash[GIT_HASH_SHA1_SIZE];
 	git_oid oid = {{0}};
 	bool append_hash = false;
@@ -51,7 +51,7 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
 	size -= 4;
 
 	if (append_hash) {
-		if (git_buf_init(&commit_graph_buf, size + GIT_HASH_SHA1_SIZE) < 0)
+		if (git_str_init(&commit_graph_buf, size + GIT_HASH_SHA1_SIZE) < 0)
 			goto cleanup;
 		if (git_hash_buf(hash, data, size, GIT_HASH_ALGORITHM_SHA1) < 0) {
 			fprintf(stderr, "Failed to compute the SHA1 hash\n");
@@ -62,13 +62,13 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
 
 		memcpy(oid.id, hash, GIT_OID_RAWSZ);
 	} else {
-		git_buf_attach_notowned(&commit_graph_buf, (char *)data, size);
+		git_str_attach_notowned(&commit_graph_buf, (char *)data, size);
 	}
 
 	if (git_commit_graph_file_parse(
 			    &file,
-			    (const unsigned char *)git_buf_cstr(&commit_graph_buf),
-			    git_buf_len(&commit_graph_buf))
+			    (const unsigned char *)git_str_cstr(&commit_graph_buf),
+			    git_str_len(&commit_graph_buf))
 	    < 0)
 		goto cleanup;
 
@@ -78,6 +78,6 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
 
 cleanup:
 	git_commit_graph_file_close(&file);
-	git_buf_dispose(&commit_graph_buf);
+	git_str_dispose(&commit_graph_buf);
 	return 0;
 }
diff --git a/fuzzers/midx_fuzzer.c b/fuzzers/midx_fuzzer.c
index 9739f0a40..3cd609063 100644
--- a/fuzzers/midx_fuzzer.c
+++ b/fuzzers/midx_fuzzer.c
@@ -11,7 +11,6 @@
 
 #include "git2.h"
 
-#include "buffer.h"
 #include "common.h"
 #include "futils.h"
 #include "hash.h"
@@ -33,7 +32,7 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
 {
 	git_midx_file idx = {{0}};
 	git_midx_entry e;
-	git_buf midx_buf = GIT_BUF_INIT;
+	git_str midx_buf = GIT_STR_INIT;
 	unsigned char hash[GIT_HASH_SHA1_SIZE];
 	git_oid oid = {{0}};
 	bool append_hash = false;
@@ -51,7 +50,7 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
 	size -= 4;
 
 	if (append_hash) {
-		if (git_buf_init(&midx_buf, size + GIT_HASH_SHA1_SIZE) < 0)
+		if (git_str_init(&midx_buf, size + GIT_HASH_SHA1_SIZE) < 0)
 			goto cleanup;
 		if (git_hash_buf(hash, data, size, GIT_HASH_ALGORITHM_SHA1) < 0) {
 			fprintf(stderr, "Failed to compute the SHA1 hash\n");
@@ -62,10 +61,10 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
 
 		memcpy(oid.id, hash, GIT_OID_RAWSZ);
 	} else {
-		git_buf_attach_notowned(&midx_buf, (char *)data, size);
+		git_str_attach_notowned(&midx_buf, (char *)data, size);
 	}
 
-	if (git_midx_parse(&idx, (const unsigned char *)git_buf_cstr(&midx_buf), git_buf_len(&midx_buf)) < 0)
+	if (git_midx_parse(&idx, (const unsigned char *)git_str_cstr(&midx_buf), git_str_len(&midx_buf)) < 0)
 		goto cleanup;
 
 	/* Search for any oid, just to exercise that codepath. */
@@ -74,6 +73,6 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
 
 cleanup:
 	git_midx_close(&idx);
-	git_buf_dispose(&midx_buf);
+	git_str_dispose(&midx_buf);
 	return 0;
 }
diff --git a/fuzzers/packfile_fuzzer.c b/fuzzers/packfile_fuzzer.c
index 50c115755..f739b9563 100644
--- a/fuzzers/packfile_fuzzer.c
+++ b/fuzzers/packfile_fuzzer.c
@@ -12,7 +12,7 @@
 #include "git2.h"
 #include "git2/sys/mempack.h"
 #include "common.h"
-#include "buffer.h"
+#include "str.h"
 
 static git_odb *odb = NULL;
 static git_odb_backend *mempack = NULL;
@@ -53,7 +53,7 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
 {
 	git_indexer_progress stats = {0, 0};
 	git_indexer *indexer = NULL;
-	git_buf path = GIT_BUF_INIT;
+	git_str path = GIT_STR_INIT;
 	git_oid oid;
 	bool append_hash = false;
 
@@ -99,19 +99,19 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
 	if (git_indexer_commit(indexer, &stats) < 0)
 		goto cleanup;
 
-	if (git_buf_printf(&path, "pack-%s.idx", git_oid_tostr_s(git_indexer_hash(indexer))) < 0)
+	if (git_str_printf(&path, "pack-%s.idx", git_oid_tostr_s(git_indexer_hash(indexer))) < 0)
 		goto cleanup;
-	p_unlink(git_buf_cstr(&path));
+	p_unlink(git_str_cstr(&path));
 
-	git_buf_clear(&path);
+	git_str_clear(&path);
 
-	if (git_buf_printf(&path, "pack-%s.pack", git_oid_tostr_s(git_indexer_hash(indexer))) < 0)
+	if (git_str_printf(&path, "pack-%s.pack", git_oid_tostr_s(git_indexer_hash(indexer))) < 0)
 		goto cleanup;
-	p_unlink(git_buf_cstr(&path));
+	p_unlink(git_str_cstr(&path));
 
 cleanup:
 	git_mempack_reset(mempack);
 	git_indexer_free(indexer);
-	git_buf_dispose(&path);
+	git_str_dispose(&path);
 	return 0;
 }
diff --git a/fuzzers/standalone_driver.c b/fuzzers/standalone_driver.c
index 90e701333..88c8cfbda 100644
--- a/fuzzers/standalone_driver.c
+++ b/fuzzers/standalone_driver.c
@@ -16,7 +16,7 @@ extern int LLVMFuzzerInitialize(int *argc, char ***argv);
 
 static int run_one_file(const char *filename)
 {
-	git_buf buf = GIT_BUF_INIT;
+	git_str buf = GIT_STR_INIT;
 	int error = 0;
 
 	if (git_futils_readbuffer(&buf, filename) < 0) {
@@ -27,7 +27,7 @@ static int run_one_file(const char *filename)
 
 	LLVMFuzzerTestOneInput((const unsigned char *)buf.ptr, buf.size);
 exit:
-	git_buf_dispose(&buf);
+	git_str_dispose(&buf);
 	return error;
 }