Merge pull request #1916 from libgit2/simplify-examples

Fix examples to make the important stuff more obvious

examples/CMakeLists.txt

@@ -9,6 +9,8 @@ ENDIF()
 FILE(GLOB SRC_EXAMPLE_APPS RELATIVE ${CMAKE_CURRENT_SOURCE_DIR} *.c)
 FOREACH(src_app ${SRC_EXAMPLE_APPS})
 	STRING(REPLACE ".c" "" app_name ${src_app})
-	ADD_EXECUTABLE(${app_name} ${src_app})
-	TARGET_LINK_LIBRARIES(${app_name} git2)
+	IF(NOT ${app_name} STREQUAL "common")
+		ADD_EXECUTABLE(${app_name} ${src_app} "common.c")
+		TARGET_LINK_LIBRARIES(${app_name} git2)
+	ENDIF()
 ENDFOREACH()

examples/Makefile

@@ -8,7 +8,7 @@ APPS = general showindex diff rev-list cat-file status log rev-parse init
 all: $(APPS)
 
 % : %.c
-	$(CC) -o $@ $(CFLAGS) $< $(LFLAGS)
+	$(CC) -o $@ common.c $(CFLAGS) $< $(LFLAGS)
 
 clean:
 	$(RM) $(APPS)

examples/README.md

 libgit2 examples
 ================
 
-These examples are meant as thin, easy-to-read snippets for Docurium
-(https://github.com/github/docurium) rather than full-blown
-implementations of Git commands.  They are not vetted as carefully
-for bugs, error handling, or cross-platform compatibility as the
-rest of the code in libgit2, so copy with some caution.
+These examples are a mixture of basic emulation of core Git command line
+functions and simple snippets demonstrating libgit2 API usage (for use
+with Docurium).  As a whole, they are not vetted carefully for bugs, error
+handling, and cross-platform compatibility in the same manner as the rest
+of the code in libgit2, so copy with caution.
 
-For HTML versions, check "Examples" at http://libgit2.github.com/libgit2
+That being said, you are welcome to copy code from these examples as
+desired when using libgit2.
 
+For annotated HTML versions, see the "Examples" section of:
+
+    http://libgit2.github.com/libgit2
+
+such as:
+
+    http://libgit2.github.com/libgit2/ex/HEAD/general.html

examples/add.c

-#include <git2.h>
-#include <stdio.h>
-#include <string.h>
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#include "common.h"
 #include <assert.h>
 
 enum print_options {
@@ -14,19 +19,49 @@ struct print_payload {
 	git_repository *repo;
 };
 
-void init_array(git_strarray *array, int argc, char **argv)
+/* Forward declarations for helpers */
+static void parse_opts(int *options, int *count, int argc, char *argv[]);
+void init_array(git_strarray *array, int argc, char **argv);
+int print_matched_cb(const char *path, const char *matched_pathspec, void *payload);
+
+int main (int argc, char** argv)
 {
-	unsigned int i;
+	git_index_matched_path_cb matched_cb = NULL;
+	git_repository *repo = NULL;
+	git_index *index;
+	git_strarray array = {0};
+	int options = 0, count = 0;
+	struct print_payload payload = {0};
 
-	array->count = argc;
-	array->strings = malloc(sizeof(char*) * array->count);
-	assert(array->strings!=NULL);
+	git_threads_init();
 
-	for(i=0; i<array->count; i++) {
-		array->strings[i]=argv[i];
+	parse_opts(&options, &count, argc, argv);
+
+	init_array(&array, argc-count, argv+count);
+
+	check_lg2(git_repository_open(&repo, "."), "No git repository", NULL);
+	check_lg2(git_repository_index(&index, repo), "Could not open repository index", NULL);
+
+	if (options&VERBOSE || options&SKIP) {
+		matched_cb = &print_matched_cb;
 	}
 
-	return;
+	payload.options = options;
+	payload.repo = repo;
+
+	if (options&UPDATE) {
+		git_index_update_all(index, &array, matched_cb, &payload);
+	} else {
+		git_index_add_all(index, &array, 0, matched_cb, &payload);
+	}
+
+	git_index_write(index);
+	git_index_free(index);
+	git_repository_free(repo);
+
+	git_threads_shutdown();
+
+	return 0;
 }
 
 int print_matched_cb(const char *path, const char *matched_pathspec, void *payload)
@@ -55,36 +90,46 @@ int print_matched_cb(const char *path, const char *matched_pathspec, void *paylo
 	return ret;
 }
 
+void init_array(git_strarray *array, int argc, char **argv)
+{
+	unsigned int i;
+
+	array->count = argc;
+	array->strings = malloc(sizeof(char*) * array->count);
+	assert(array->strings!=NULL);
+
+	for(i=0; i<array->count; i++) {
+		array->strings[i]=argv[i];
+	}
+
+	return;
+}
+
 void print_usage(void)
 {
 	fprintf(stderr, "usage: add [options] [--] file-spec [file-spec] [...]\n\n");
 	fprintf(stderr, "\t-n, --dry-run    dry run\n");
 	fprintf(stderr, "\t-v, --verbose    be verbose\n");
 	fprintf(stderr, "\t-u, --update     update tracked files\n");
+	exit(1);
 }
 
-
-int main (int argc, char** argv)
+static void parse_opts(int *options, int *count, int argc, char *argv[])
 {
-	git_index_matched_path_cb matched_cb = NULL;
-	git_repository *repo = NULL;
-	git_index *index;
-	git_strarray array = {0};
-	int i, options = 0;
-	struct print_payload payload = {0};
+	int i;
 
 	for (i = 1; i < argc; ++i) {
 		if (argv[i][0] != '-') {
 			break;
 		}
 		else if(!strcmp(argv[i], "--verbose") || !strcmp(argv[i], "-v")) {
-			options |= VERBOSE;
+			*options |= VERBOSE;
 		}
 		else if(!strcmp(argv[i], "--dry-run") || !strcmp(argv[i], "-n")) {
-			options |= SKIP;
+			*options |= SKIP;
 		}
 		else if(!strcmp(argv[i], "--update") || !strcmp(argv[i], "-u")) {
-			options |= UPDATE;
+			*options |= UPDATE;
 		}
 		else if(!strcmp(argv[i], "-h")) {
 			print_usage();
@@ -97,47 +142,11 @@ int main (int argc, char** argv)
 		else {
 			fprintf(stderr, "Unsupported option %s.\n", argv[i]);
 			print_usage();
-			return 1;
 		}
 	}
 
-	if (argc<=i) {
+	if (argc<=i)
 		print_usage();
-		return 1;
-	}
 
-	git_threads_init();
-
-	init_array(&array, argc-i, argv+i);
-
-	if (git_repository_open(&repo, ".") < 0) {
-		fprintf(stderr, "No git repository\n");
-		return 1;
-	}
-
-	if (git_repository_index(&index, repo) < 0) {
-		fprintf(stderr, "Could not open repository index\n");
-		return 1;
-	}
-
-	if (options&VERBOSE || options&SKIP) {
-		matched_cb = &print_matched_cb;
-	}
-
-	payload.options = options;
-	payload.repo = repo;
-
-	if (options&UPDATE) {
-		git_index_update_all(index, &array, matched_cb, &payload);
-	} else {
-		git_index_add_all(index, &array, 0, matched_cb, &payload);
-	}
-
-	git_index_write(index);
-	git_index_free(index);
-	git_repository_free(repo);
-
-	git_threads_shutdown();
-
-	return 0;
+	*count = i;
 }

examples/cat-file.c

-#include <stdio.h>
-#include <git2.h>
-#include <stdlib.h>
-#include <string.h>
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
 
-static git_repository *g_repo;
-
-static void check(int error, const char *message)
-{
-	if (error) {
-		fprintf(stderr, "%s (%d)\n", message, error);
-		exit(1);
-	}
-}
-
-static void usage(const char *message, const char *arg)
-{
-	if (message && arg)
-		fprintf(stderr, "%s: %s\n", message, arg);
-	else if (message)
-		fprintf(stderr, "%s\n", message);
-	fprintf(stderr, "usage: cat-file (-t | -s | -e | -p) [<options>] <object>\n");
-	exit(1);
-}
-
-static int check_str_param(
-	const char *arg, const char *pattern, const char **val)
-{
-	size_t len = strlen(pattern);
-	if (strncmp(arg, pattern, len))
-		return 0;
-	*val = (const char *)(arg + len);
-	return 1;
-}
+#include "common.h"
 
 static void print_signature(const char *header, const git_signature *sig)
 {
@@ -57,12 +31,14 @@ static void print_signature(const char *header, const git_signature *sig)
 		   sign, hours, minutes);
 }
 
+/** Printing out a blob is simple, get the contents and print */
 static void show_blob(const git_blob *blob)
 {
 	/* ? Does this need crlf filtering? */
 	fwrite(git_blob_rawcontent(blob), git_blob_rawsize(blob), 1, stdout);
 }
 
+/** Show each entry with its type, id and attributes */
 static void show_tree(const git_tree *tree)
 {
 	size_t i, max_i = (int)git_tree_entrycount(tree);
@@ -81,6 +57,9 @@ static void show_tree(const git_tree *tree)
 	}
 }
 
+/**
+ * Commits and tags have a few interesting fields in their header.
+ */
 static void show_commit(const git_commit *commit)
 {
 	unsigned int i, max_i;
@@ -123,53 +102,34 @@ enum {
 	SHOW_PRETTY = 4
 };
 
+/* Forward declarations for option-parsing helper */
+struct opts {
+	const char *dir;
+	const char *rev;
+	int action;
+	int verbose;
+};
+static void parse_opts(struct opts *o, int argc, char *argv[]);
+
+
+/** Entry point for this command */
 int main(int argc, char *argv[])
 {
-	const char *dir = ".", *rev = NULL;
-	int i, action = 0, verbose = 0;
+	git_repository *repo;
+	struct opts o = { ".", NULL, 0, 0 };
 	git_object *obj = NULL;
 	char oidstr[GIT_OID_HEXSZ + 1];
 
 	git_threads_init();
 
-	for (i = 1; i < argc; ++i) {
-		char *a = argv[i];
-
-		if (a[0] != '-') {
-			if (rev != NULL)
-				usage("Only one rev should be provided", NULL);
-			else
-				rev = a;
-		}
-		else if (!strcmp(a, "-t"))
-			action = SHOW_TYPE;
-		else if (!strcmp(a, "-s"))
-			action = SHOW_SIZE;
-		else if (!strcmp(a, "-e"))
-			action = SHOW_NONE;
-		else if (!strcmp(a, "-p"))
-			action = SHOW_PRETTY;
-		else if (!strcmp(a, "-q"))
-			verbose = 0;
-		else if (!strcmp(a, "-v"))
-			verbose = 1;
-		else if (!strcmp(a, "--help") || !strcmp(a, "-h"))
-			usage(NULL, NULL);
-		else if (!check_str_param(a, "--git-dir=", &dir))
-			usage("Unknown option", a);
-	}
-
-	if (!action || !rev)
-		usage(NULL, NULL);
+	parse_opts(&o, argc, argv);
 
-	check(git_repository_open_ext(&g_repo, dir, 0, NULL),
-		"Could not open repository");
+	check_lg2(git_repository_open_ext(&repo, o.dir, 0, NULL),
+			"Could not open repository", NULL);
+	check_lg2(git_revparse_single(&obj, repo, o.rev),
+			"Could not resolve", o.rev);
 
-	if (git_revparse_single(&obj, g_repo, rev) < 0) {
-		fprintf(stderr, "Could not resolve '%s'\n", rev);
-		exit(1);
-	}
-	if (verbose) {
+	if (o.verbose) {
 		char oidstr[GIT_OID_HEXSZ + 1];
 		git_oid_tostr(oidstr, sizeof(oidstr), git_object_id(obj));
 
@@ -177,7 +137,7 @@ int main(int argc, char *argv[])
 			git_object_type2string(git_object_type(obj)), oidstr);
 	}
 
-	switch (action) {
+	switch (o.action) {
 	case SHOW_TYPE:
 		printf("%s\n", git_object_type2string(git_object_type(obj)));
 		break;
@@ -185,9 +145,9 @@ int main(int argc, char *argv[])
 		git_odb *odb;
 		git_odb_object *odbobj;
 
-		check(git_repository_odb(&odb, g_repo), "Could not open ODB");
-		check(git_odb_read(&odbobj, odb, git_object_id(obj)),
-			"Could not find obj");
+		check_lg2(git_repository_odb(&odb, repo), "Could not open ODB", NULL);
+		check_lg2(git_odb_read(&odbobj, odb, git_object_id(obj)),
+			"Could not find obj", NULL);
 
 		printf("%ld\n", (long)git_odb_object_size(odbobj));
 
@@ -221,9 +181,59 @@ int main(int argc, char *argv[])
 	}
 
 	git_object_free(obj);
-	git_repository_free(g_repo);
+	git_repository_free(repo);
 
 	git_threads_shutdown();
 
 	return 0;
 }
+
+/** Print out usage information */
+static void usage(const char *message, const char *arg)
+{
+	if (message && arg)
+		fprintf(stderr, "%s: %s\n", message, arg);
+	else if (message)
+		fprintf(stderr, "%s\n", message);
+	fprintf(stderr,
+			"usage: cat-file (-t | -s | -e | -p) [-v] [-q] "
+			"[-h|--help] [--git-dir=<dir>] <object>\n");
+	exit(1);
+}
+
+/** Parse the command-line options taken from git */
+static void parse_opts(struct opts *o, int argc, char *argv[])
+{
+	struct args_info args = ARGS_INFO_INIT;
+
+	for (args.pos = 1; args.pos < argc; ++args.pos) {
+		char *a = argv[args.pos];
+
+		if (a[0] != '-') {
+			if (o->rev != NULL)
+				usage("Only one rev should be provided", NULL);
+			else
+				o->rev = a;
+		}
+		else if (!strcmp(a, "-t"))
+			o->action = SHOW_TYPE;
+		else if (!strcmp(a, "-s"))
+			o->action = SHOW_SIZE;
+		else if (!strcmp(a, "-e"))
+			o->action = SHOW_NONE;
+		else if (!strcmp(a, "-p"))
+			o->action = SHOW_PRETTY;
+		else if (!strcmp(a, "-q"))
+			o->verbose = 0;
+		else if (!strcmp(a, "-v"))
+			o->verbose = 1;
+		else if (!strcmp(a, "--help") || !strcmp(a, "-h"))
+			usage(NULL, NULL);
+		else if (!match_str_arg(&o->dir, &args, "--git-dir"))
+			usage("Unknown option", a);
+	}
+
+	if (!o->action || !o->rev)
+		usage(NULL, NULL);
+
+}

examples/common.c

+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#include "common.h"
+
+void check_lg2(int error, const char *message, const char *extra)
+{
+	const git_error *lg2err;
+	const char *lg2msg = "", *lg2spacer = "";
+
+	if (!error)
+		return;
+
+	if ((lg2err = giterr_last()) != NULL && lg2err->message != NULL) {
+		lg2msg = lg2err->message;
+		lg2spacer = " - ";
+	}
+
+	if (extra)
+		fprintf(stderr, "%s '%s' [%d]%s%s\n",
+			message, extra, error, lg2spacer, lg2msg);
+	else
+		fprintf(stderr, "%s [%d]%s%s\n",
+			message, error, lg2spacer, lg2msg);
+
+	exit(1);
+}
+
+void fatal(const char *message, const char *extra)
+{
+	if (extra)
+		fprintf(stderr, "%s %s\n", message, extra);
+	else
+		fprintf(stderr, "%s\n", message);
+
+	exit(1);
+}
+
+size_t is_prefixed(const char *str, const char *pfx)
+{
+	size_t len = strlen(pfx);
+	return strncmp(str, pfx, len) ? 0 : len;
+}
+
+int match_str_arg(
+	const char **out, struct args_info *args, const char *opt)
+{
+	const char *found = args->argv[args->pos];
+	size_t len = is_prefixed(found, opt);
+
+	if (!len)
+		return 0;
+
+	if (!found[len]) {
+		if (args->pos + 1 == args->argc)
+			fatal("expected value following argument", opt);
+		args->pos += 1;
+		*out = args->argv[args->pos];
+		return 1;
+	}
+
+	if (found[len] == '=') {
+		*out = found + len + 1;
+		return 1;
+	}
+
+	return 0;
+}
+
+static const char *match_numeric_arg(struct args_info *args, const char *opt)
+{
+	const char *found = args->argv[args->pos];
+	size_t len = is_prefixed(found, opt);
+
+	if (!len)
+		return NULL;
+
+	if (!found[len]) {
+		if (args->pos + 1 == args->argc)
+			fatal("expected numeric value following argument", opt);
+		args->pos += 1;
+		found = args->argv[args->pos];
+	} else {
+		found = found + len;
+		if (*found == '=')
+			found++;
+	}
+
+	return found;
+}
+
+int match_uint16_arg(
+	uint16_t *out, struct args_info *args, const char *opt)
+{
+	const char *found = match_numeric_arg(args, opt);
+	uint16_t val;
+	char *endptr = NULL;
+
+	if (!found)
+		return 0;
+
+	val = (uint16_t)strtoul(found, &endptr, 0);
+	if (!endptr || *endptr != '\0')
+		fatal("expected number after argument", opt);
+
+	if (out)
+		*out = val;
+	return 1;
+}
+
+static int match_int_internal(
+	int *out, const char *str, int allow_negative, const char *opt)
+{
+	char *endptr = NULL;
+	int	  val = (int)strtol(str, &endptr, 10);
+
+	if (!endptr || *endptr != '\0')
+		fatal("expected number", opt);
+	else if (val < 0 && !allow_negative)
+		fatal("negative values are not allowed", opt);
+
+	if (out)
+		*out = val;
+
+	return 1;
+}
+
+int is_integer(int *out, const char *str, int allow_negative)
+{
+	return match_int_internal(out, str, allow_negative, NULL);
+}
+
+int match_int_arg(
+	int *out, struct args_info *args, const char *opt, int allow_negative)
+{
+	const char *found = match_numeric_arg(args, opt);
+	if (!found)
+		return 0;
+	return match_int_internal(out, found, allow_negative, opt);
+}
+
+int diff_output(
+	const git_diff_delta *d,
+	const git_diff_hunk *h,
+	const git_diff_line *l,
+	void *p)
+{
+	FILE *fp = p;
+
+	(void)d; (void)h;
+
+	if (!fp)
+		fp = stdout;
+
+	if (l->origin == GIT_DIFF_LINE_CONTEXT ||
+		l->origin == GIT_DIFF_LINE_ADDITION ||
+		l->origin == GIT_DIFF_LINE_DELETION)
+		fputc(l->origin, fp);
+
+	fwrite(l->content, 1, l->content_len, fp);
+
+	return 0;
+}
+
+void treeish_to_tree(
+	git_tree **out, git_repository *repo, const char *treeish)
+{
+	git_object *obj = NULL;
+
+	check_lg2(
+		git_revparse_single(&obj, repo, treeish),
+		"looking up object", treeish);
+
+	check_lg2(
+		git_object_peel((git_object **)out, obj, GIT_OBJ_TREE),
+		"resolving object to tree", treeish);
+
+	git_object_free(obj);
+}
+

examples/common.h

+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <git2.h>
+
+/**
+ * Check libgit2 error code, printing error to stderr on failure and
+ * exiting the program.
+ */
+extern void check_lg2(int error, const char *message, const char *extra);
+
+/**
+ * Exit the program, printing error to stderr
+ */
+extern void fatal(const char *message, const char *extra);
+
+/**
+ * Check if a string has the given prefix.  Returns 0 if not prefixed
+ * or the length of the prefix if it is.
+ */
+extern size_t is_prefixed(const char *str, const char *pfx);
+
+/**
+ * Match an integer string, returning 1 if matched, 0 if not.
+ */
+extern int is_integer(int *out, const char *str, int allow_negative);
+
+struct args_info {
+	int    argc;
+	char **argv;
+	int    pos;
+};
+#define ARGS_INFO_INIT { argc, argv, 0 }
+
+/**
+ * Check current `args` entry against `opt` string.  If it matches
+ * exactly, take the next arg as a string; if it matches as a prefix with
+ * an equal sign, take the remainder as a string; otherwise return 0.
+ */
+extern int match_str_arg(
+	const char **out, struct args_info *args, const char *opt);
+
+/**
+ * Check current `args` entry against `opt` string parsing as uint16.  If
+ * `opt` matches exactly, take the next arg as a uint16_t value; if `opt`
+ * is a prefix (equal sign optional), take the remainder of the arg as a
+ * uint16_t value; otherwise return 0.
+ */
+extern int match_uint16_arg(
+	uint16_t *out, struct args_info *args, const char *opt);
+
+/**
+ * Check current `args` entry against `opt` string parsing as int.  If
+ * `opt` matches exactly, take the next arg as an int value; if it matches
+ * as a prefix (equal sign optional), take the remainder of the arg as a
+ * int value; otherwise return 0.
+ */
+extern int match_int_arg(
+	int *out, struct args_info *args, const char *opt, int allow_negative);
+
+/**
+ * Basic output function for plain text diff output
+ * Pass `FILE*` such as `stdout` or `stderr` as payload (or NULL == `stdout`)
+ */
+extern int diff_output(
+	const git_diff_delta*, const git_diff_hunk*, const git_diff_line*, void*);
+
+/**
+ * Convert a treeish argument to an actual tree; this will call check_lg2
+ * and exit the program if `treeish` cannot be resolved to a tree
+ */
+extern void treeish_to_tree(
+	git_tree **out, git_repository *repo, const char *treeish);

examples/network/fetch.c

@@ -47,6 +47,11 @@ exit:
 	return &data->ret;
 }
 
+/**
+ * This function gets called for each remote-tracking branch that gets
+ * updated. The message we output depends on whether it's a new one or
+ * an update.
+ */
 static int update_cb(const char *refname, const git_oid *a, const git_oid *b, void *data)
 {
 	char a_str[GIT_OID_HEXSZ+1], b_str[GIT_OID_HEXSZ+1];
@@ -66,6 +71,7 @@ static int update_cb(const char *refname, const git_oid *a, const git_oid *b, vo
 	return 0;
 }
 
+/** Entry point for this command */
 int fetch(git_repository *repo, int argc, char **argv)
 {
 	git_remote *remote = NULL;
@@ -130,6 +136,11 @@ int fetch(git_repository *repo, int argc, char **argv)
 	pthread_join(worker, NULL);
 #endif
 
+	/**
+	 * If there are local objects (we got a thin pack), then tell
+	 * the user how many objects we saved from having to cross the
+	 * network.
+	 */
 	if (stats->local_objects > 0) {
 		printf("\rReceived %d/%d objects in %zu bytes (used %d local objects)\n",
 		       stats->indexed_objects, stats->total_objects, stats->received_bytes, stats->local_objects);

examples/network/ls-remote.c

@@ -4,6 +4,7 @@
 #include <string.h>
 #include "common.h"
 
+/** Callback to show each item */
 static int show_ref__cb(git_remote_head *head, void *payload)
 {
 	char oid[GIT_OID_HEXSZ + 1] = {0};
@@ -28,6 +29,10 @@ static int use_remote(git_repository *repo, char *name)
 			goto cleanup;
 	}
 
+	/**
+	 * Connect to the remote and call the printing function for
+	 * each of the remote references.
+	 */
 	callbacks.credentials = cred_acquire_cb;
 	git_remote_set_callbacks(remote, &callbacks);
 
@@ -42,9 +47,7 @@ cleanup:
 	return error;
 }
 
-// This gets called to do the work. The remote can be given either as
-// the name of a configured remote or an URL.
-
+/** Entry point for this command */
 int ls_remote(git_repository *repo, int argc, char **argv)
 {
 	int error;

examples/rev-list.c

-#include <stdio.h>
-#include <string.h>
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
 
-#include <git2.h>
+#include "common.h"
 
-static void check_error(int error_code, const char *action)
+static int revwalk_parseopts(git_repository *repo, git_revwalk *walk, int nopts, char **opts);
+
+int main (int argc, char **argv)
 {
-	if (!error_code)
-		return;
+	git_repository *repo;
+	git_revwalk *walk;
+	git_oid oid;
+	char buf[41];
+
+	git_threads_init();
 
-	const git_error *error = giterr_last();
-	fprintf(stderr, "Error %d %s: %s\n", -error_code, action,
-	        (error && error->message) ? error->message : "???");
-	exit(1);
+	check_lg2(git_repository_open_ext(&repo, ".", 0, NULL), "opening repository", NULL);
+	check_lg2(git_revwalk_new(&walk, repo), "allocating revwalk", NULL);
+	check_lg2(revwalk_parseopts(repo, walk, argc-1, argv+1), "parsing options", NULL);
+
+	while (!git_revwalk_next(&oid, walk)) {
+		git_oid_fmt(buf, &oid);
+		buf[40] = '\0';
+		printf("%s\n", buf);
+	}
+
+	git_threads_shutdown();
+	return 0;
 }
 
 static int push_commit(git_revwalk *walk, const git_oid *oid, int hide)
@@ -93,27 +111,3 @@ static int revwalk_parseopts(git_repository *repo, git_revwalk *walk, int nopts,
 	return 0;
 }
 
-int main (int argc, char **argv)
-{
-	int error;
-	git_repository *repo;
-	git_revwalk *walk;
-	git_oid oid;
-	char buf[41];
-
-	error = git_repository_open_ext(&repo, ".", 0, NULL);
-	check_error(error, "opening repository");
-
-	error = git_revwalk_new(&walk, repo);
-	check_error(error, "allocating revwalk");
-	error = revwalk_parseopts(repo, walk, argc-1, argv+1);
-	check_error(error, "parsing options");
-
-	while (!git_revwalk_next(&oid, walk)) {
-		git_oid_fmt(buf, &oid);
-		buf[40] = '\0';
-		printf("%s\n", buf);
-	}
-
-	return 0;
-}

examples/rev-parse.c

-#include <stdio.h>
-#include <git2.h>
-#include <stdlib.h>
-#include <string.h>
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
 
-static void check(int error, const char *message, const char *arg)
+#include "common.h"
+
+/** Forward declarations for helpers. */
+struct parse_state {
+	git_repository *repo;
+	const char *repodir;
+	const char *spec;
+	int not;
+};
+static void parse_opts(struct parse_state *ps, int argc, char *argv[]);
+static int parse_revision(struct parse_state *ps);
+
+
+int main(int argc, char *argv[])
 {
-	if (!error)
-		return;
-	if (arg)
-		fprintf(stderr, "%s %s (%d)\n", message, arg, error);
-	else
-		fprintf(stderr, "%s(%d)\n", message, error);
-	exit(1);
+	struct parse_state ps = {0};
+
+	git_threads_init();
+	parse_opts(&ps, argc, argv);
+
+	check_lg2(parse_revision(&ps), "Parsing", NULL);
+
+	git_repository_free(ps.repo);
+	git_threads_shutdown();
+
+	return 0;
 }
 
 static void usage(const char *message, const char *arg)
@@ -24,13 +43,25 @@ static void usage(const char *message, const char *arg)
 	exit(1);
 }
 
-struct parse_state {
-	git_repository *repo;
-	const char *repodir;
-	int not;
-};
+static void parse_opts(struct parse_state *ps, int argc, char *argv[])
+{
+	struct args_info args = ARGS_INFO_INIT;
 
-static int parse_revision(struct parse_state *ps, const char *revstr)
+	for (args.pos=1; args.pos < argc; ++args.pos) {
+		const char *a = argv[args.pos];
+
+		if (a[0] != '-') {
+			if (ps->spec)
+				usage("Too many specs", a);
+			ps->spec = a;
+		} else if (!strcmp(a, "--not"))
+			ps->not = !ps->not;
+		else if (!match_str_arg(&ps->repodir, &args, "--git-dir"))
+			usage("Cannot handle argument", a);
+	}
+}
+
+static int parse_revision(struct parse_state *ps)
 {
 	git_revspec rs;
 	char str[GIT_OID_HEXSZ + 1];
@@ -38,11 +69,11 @@ static int parse_revision(struct parse_state *ps, const char *revstr)
 	if (!ps->repo) {
 		if (!ps->repodir)
 			ps->repodir = ".";
-		check(git_repository_open_ext(&ps->repo, ps->repodir, 0, NULL),
+		check_lg2(git_repository_open_ext(&ps->repo, ps->repodir, 0, NULL),
 			"Could not open repository from", ps->repodir);
 	}
 
-	check(git_revparse(&rs, ps->repo, revstr), "Could not parse", revstr);
+	check_lg2(git_revparse(&rs, ps->repo, ps->spec), "Could not parse", ps->spec);
 
 	if ((rs.flags & GIT_REVPARSE_SINGLE) != 0) {
 		git_oid_tostr(str, sizeof(str), git_object_id(rs.from));
@@ -56,9 +87,9 @@ static int parse_revision(struct parse_state *ps, const char *revstr)
 
 		if ((rs.flags & GIT_REVPARSE_MERGE_BASE) != 0) {
 			git_oid base;
-			check(git_merge_base(&base, ps->repo,
-				git_object_id(rs.from), git_object_id(rs.to)),
-				"Could not find merge base", revstr);
+			check_lg2(git_merge_base(&base, ps->repo,
+						git_object_id(rs.from), git_object_id(rs.to)),
+					"Could not find merge base", ps->spec);
 
 			git_oid_tostr(str, sizeof(str), &base);
 			printf("%s\n", str);
@@ -69,38 +100,9 @@ static int parse_revision(struct parse_state *ps, const char *revstr)
 		git_object_free(rs.from);
 	}
 	else {
-		check(0, "Invalid results from git_revparse", revstr);
+		fatal("Invalid results from git_revparse", ps->spec);
 	}
 
 	return 0;
 }
 
-int main(int argc, char *argv[])
-{
-	int i;
-	char *a;
-	struct parse_state ps;
-
-	git_threads_init();
-
-	memset(&ps, 0, sizeof(ps));
-
-	for (i = 1; i < argc; ++i) {
-		a = argv[i];
-
-		if (a[0] != '-') {
-			if (parse_revision(&ps, a) != 0)
-				break;
-		} else if (!strcmp(a, "--not"))
-			ps.not = !ps.not;
-		else if (!strncmp(a, "--git-dir=", strlen("--git-dir=")))
-			ps.repodir = a + strlen("--git-dir=");
-		else
-			usage("Cannot handle argument", a);
-	}
-
-	git_repository_free(ps.repo);
-	git_threads_shutdown();
-
-	return 0;
-}

examples/showindex.c

-#include <git2.h>
-#include <stdio.h>
-#include <string.h>
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#include "common.h"
 
 int main (int argc, char** argv)
 {
-	git_repository *repo = NULL;
 	git_index *index;
 	unsigned int i, ecount;
 	char *dir = ".";
@@ -14,28 +18,19 @@ int main (int argc, char** argv)
 
 	git_threads_init();
 
+	if (argc > 2)
+		fatal("usage: showindex [<repo-dir>]", NULL);
 	if (argc > 1)
 		dir = argv[1];
-	if (!dir || argc > 2) {
-		fprintf(stderr, "usage: showindex [<repo-dir>]\n");
-		return 1;
-	}
 
 	dirlen = strlen(dir);
 	if (dirlen > 5 && strcmp(dir + dirlen - 5, "index") == 0) {
-		if (git_index_open(&index, dir) < 0) {
-			fprintf(stderr, "could not open index: %s\n", dir);
-			return 1;
-		}
+		check_lg2(git_index_open(&index, dir), "could not open index", dir);
 	} else {
-		if (git_repository_open_ext(&repo, dir, 0, NULL) < 0) {
-			fprintf(stderr, "could not open repository: %s\n", dir);
-			return 1;
-		}
-		if (git_repository_index(&index, repo) < 0) {
-			fprintf(stderr, "could not open repository index\n");
-			return 1;
-		}
+		git_repository *repo;
+		check_lg2(git_repository_open_ext(&repo, dir, 0, NULL), "could not open repository", dir);
+		check_lg2(git_repository_index(&index, repo), "could not open repository index", NULL);
+		git_repository_free(repo);
 	}
 
 	git_index_read(index);
@@ -62,10 +57,7 @@ int main (int argc, char** argv)
 	}
 
 	git_index_free(index);
-	git_repository_free(repo);
-
 	git_threads_shutdown();
 
 	return 0;
 }
-