Clear up warnings from cppcheck

The cppcheck static analyzer generates warnings for a bunch of
places in the libgit2 code base.  All the ones fixed in this
commit are actually false positives, but I've reorganized the
code to hopefully make it easier for static analysis tools to
correctly understand the structure.  I wouldn't do this if I
felt like it was making the code harder to read or worse for
humans, but in this case, these fixes don't seem too bad and will
hopefully make it easier for better analysis tools to get at any
real issues.

src/checkout.c

@@ -64,6 +64,7 @@ static int checkout_notify(
 {
 	git_diff_file wdfile;
 	const git_diff_file *baseline = NULL, *target = NULL, *workdir = NULL;
+	const char *path = NULL;
 
 	if (!data->opts.notify_cb)
 		return 0;
@@ -81,6 +82,8 @@ static int checkout_notify(
 		wdfile.mode = wditem->mode;
 
 		workdir = &wdfile;
+
+		path = wditem->path;
 	}
 
 	if (delta) {
@@ -101,11 +104,12 @@ static int checkout_notify(
 			baseline = &delta->old_file;
 			break;
 		}
+
+		path = delta->old_file.path;
 	}
 
 	return data->opts.notify_cb(
-		why, delta ? delta->old_file.path : wditem->path,
-		baseline, target, workdir, data->opts.notify_payload);
+		why, path, baseline, target, workdir, data->opts.notify_payload);
 }
 
 static bool checkout_is_workdir_modified(
@@ -683,7 +687,7 @@ static int blob_content_to_file(
 {
 	int error = -1, nb_filters = 0;
 	mode_t file_mode = opts->file_mode;
-	bool dont_free_filtered = false;
+	bool dont_free_filtered;
 	git_buf unfiltered = GIT_BUF_INIT, filtered = GIT_BUF_INIT;
 	git_vector filters = GIT_VECTOR_INIT;
 

src/diff_output.c

@@ -1280,14 +1280,15 @@ static void set_data_from_buffer(
 {
 	file->size = (git_off_t)buffer_len;
 	file->mode = 0644;
-
-	if (!buffer)
-		file->flags |= GIT_DIFF_FILE_NO_DATA;
-	else
-		git_odb_hash(&file->oid, buffer, buffer_len, GIT_OBJ_BLOB);
-
 	map->len   = buffer_len;
+
+	if (!buffer) {
+		file->flags |= GIT_DIFF_FILE_NO_DATA;
+		map->data = NULL;
+	} else {
 		map->data = (char *)buffer;
+		git_odb_hash(&file->oid, buffer, buffer_len, GIT_OBJ_BLOB);
+	}
 }
 
 typedef struct {

src/notes.c

@@ -147,7 +147,7 @@ static int manipulate_note_in_tree_r(
 		int fanout,
 		int current_error))
 {
-	int error = -1;
+	int error;
 	git_tree *subtree = NULL, *new = NULL;
 	char subtree_name[3];
 

src/refs.c

@@ -1493,7 +1493,7 @@ int git_reference_foreach(
 	/* list all the packed references first */
 	if (list_flags & GIT_REF_PACKED) {
 		const char *ref_name;
-		void *ref;
+		void *ref = NULL;
 		GIT_UNUSED(ref);
 
 		if (packed_load(repo) < 0)

src/transports/winhttp.c

@@ -88,7 +88,7 @@ static int apply_basic_credential(HINTERNET request, git_cred *cred)
 	git_cred_userpass_plaintext *c = (git_cred_userpass_plaintext *)cred;
 	git_buf buf = GIT_BUF_INIT, raw = GIT_BUF_INIT;
 	wchar_t *wide = NULL;
-	int error = -1, wide_len;
+	int error = -1, wide_len = 0;
 
 	git_buf_printf(&raw, "%s:%s", c->username, c->password);
 

tests-clar/clar_libgit2.c

@@ -86,14 +86,18 @@ int cl_setenv(const char *name, const char *value)
 
 	git__utf8_to_16(name_utf16, GIT_WIN_PATH, name);
 
-	if (value != NULL)
+	if (value) {
 		git__utf8_to_16(value_utf16, GIT_WIN_PATH, value);
+		cl_assert(SetEnvironmentVariableW(name_utf16, value_utf16));
+	} else {
+		/* Windows XP returns 0 (failed) when passing NULL for lpValue when
+		 * lpName does not exist in the environment block. This behavior
+		 * seems to have changed in later versions. Don't check return value
+		 * of SetEnvironmentVariable when passing NULL for lpValue.
+		 */
+		SetEnvironmentVariableW(name_utf16, NULL);
+	}
 
-	/* Windows XP returns 0 (failed) when passing NULL for lpValue when lpName
-	 * does not exist in the environment block. This behavior seems to have changed
-	 * in later versions. Don't fail when SetEnvironmentVariable fails, if we passed
-	 * NULL for lpValue. */
-	cl_assert(SetEnvironmentVariableW(name_utf16, value ? value_utf16 : NULL) || !value);
 	return 0;
 }
 

tests-clar/core/env.c

@@ -74,6 +74,8 @@ void test_core_env__0(void)
 	char **val;
 
 	memset(testfile, 0, sizeof(testfile));
+	cl_assert_equal_s("", testfile);
+
 	memcpy(testfile, "testfile", 8);
 	cl_assert_equal_s("testfile", testfile);