From 8ba0ff69725251fa375520d9c69c8a053725c4b6 Mon Sep 17 00:00:00 2001
From: Russell Belfer <rb@github.com>
Date: Tue, 25 Jun 2013 15:39:44 -0700
Subject: [PATCH] rev-parse example

---
 examples/Makefile    |   2 +-
 examples/rev-parse.c | 106 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 107 insertions(+), 1 deletion(-)
 create mode 100644 examples/rev-parse.c

diff --git a/examples/Makefile b/examples/Makefile
index 6288906df..95e46f0c6 100644
--- a/examples/Makefile
+++ b/examples/Makefile
@@ -3,7 +3,7 @@
 CC = gcc
 CFLAGS = -g -I../include -I../src -Wall -Wextra -Wmissing-prototypes -Wno-missing-field-initializers
 LFLAGS = -L../build -lgit2 -lz
-APPS = general showindex diff rev-list cat-file status log
+APPS = general showindex diff rev-list cat-file status log rev-parse
 
 all: $(APPS)
 
diff --git a/examples/rev-parse.c b/examples/rev-parse.c
new file mode 100644
index 000000000..cdbb61e46
--- /dev/null
+++ b/examples/rev-parse.c
@@ -0,0 +1,106 @@
+#include <stdio.h>
+#include <git2.h>
+#include <stdlib.h>
+#include <string.h>
+
+static void check(int error, const char *message, const char *arg)
+{
+	if (!error)
+		return;
+	if (arg)
+		fprintf(stderr, "%s %s (%d)\n", message, arg, error);
+	else
+		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: rev-parse [ --option ] <args>...\n");
+	exit(1);
+}
+
+struct parse_state {
+	git_repository *repo;
+	const char *repodir;
+	int not;
+};
+
+static int parse_revision(struct parse_state *ps, const char *revstr)
+{
+	git_revspec rs;
+	char str[GIT_OID_HEXSZ + 1];
+
+	if (!ps->repo) {
+		if (!ps->repodir)
+			ps->repodir = ".";
+		check(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);
+
+	if ((rs.flags & GIT_REVPARSE_SINGLE) != 0) {
+		git_oid_tostr(str, sizeof(str), git_object_id(rs.from));
+		printf("%s\n", str);
+		git_object_free(rs.from);
+	}
+	else if ((rs.flags & GIT_REVPARSE_RANGE) != 0) {
+		git_oid_tostr(str, sizeof(str), git_object_id(rs.to));
+		printf("%s\n", str);
+		git_object_free(rs.to);
+
+		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);
+
+			git_oid_tostr(str, sizeof(str), &base);
+			printf("%s\n", str);
+		}
+
+		git_oid_tostr(str, sizeof(str), git_object_id(rs.from));
+		printf("^%s\n", str);
+		git_object_free(rs.from);
+	}
+	else {
+		check(0, "Invalid results from git_revparse", revstr);
+	}
+
+	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;
+}