thodg/libgit2

diff --git a/examples/.gitignore b/examples/.gitignore
index e40bfc2..e8e0820 100644
--- a/examples/.gitignore
+++ b/examples/.gitignore
@@ -1,4 +1,5 @@
 general
 showindex
 diff
+rev-list
 *.dSYM
diff --git a/examples/rev-list.c b/examples/rev-list.c
new file mode 100644
index 0000000..b7e466f
--- /dev/null
+++ b/examples/rev-list.c
@@ -0,0 +1,116 @@
+#include <stdio.h>
+#include <string.h>
+
+#include <git2.h>
+
+static void check_error(int error_code, const char *action)
+{
+	if (!error_code)
+		return;
+
+	const git_error *error = giterr_last();
+	fprintf(stderr, "Error %d %s: %s\n", -error_code, action,
+	        (error && error->message) ? error->message : "???");
+	exit(1);
+}
+
+static int push_commit(git_revwalk *walk, git_object *obj, int hide)
+{
+	if (hide)
+		return git_revwalk_hide(walk, git_object_id(obj));
+	else
+		return git_revwalk_push(walk, git_object_id(obj));
+}
+
+static int push_spec(git_repository *repo, git_revwalk *walk, const char *spec, int hide)
+{
+	int error;
+	git_object *obj;
+
+	if ((error = git_revparse_single(&obj, repo, spec)))
+		return error;
+	return push_commit(walk, obj, hide);
+}
+
+static int push_range(git_repository *repo, git_revwalk *walk, const char *range, int hide)
+{
+	git_object *left, *right;
+	int threedots;
+	int error = 0;
+
+	if ((error = git_revparse_rangelike(&left, &right, &threedots, repo, range)))
+		return error;
+	if (threedots) {
+		/* TODO: support "<commit>...<commit>" */
+		return GIT_EINVALIDSPEC;
+	}
+
+	if ((error = push_commit(walk, left, !hide)))
+		goto out;
+	error = push_commit(walk, right, hide);
+
+  out:
+	git_object_free(left);
+	git_object_free(right);
+	return error;
+}
+
+static int revwalk_parseopts(git_repository *repo, git_revwalk *walk, int nopts, const char *const *opts)
+{
+	int hide, i, error;
+	unsigned int sorting = GIT_SORT_NONE;
+
+	hide = 0;
+	for (i = 0; i < nopts; i++) {
+		if (!strcmp(opts[i], "--topo-order")) {
+			sorting = GIT_SORT_TOPOLOGICAL | (sorting & GIT_SORT_REVERSE);
+			git_revwalk_sorting(walk, sorting);
+		} else if (!strcmp(opts[i], "--date-order")) {
+			sorting = GIT_SORT_TIME | (sorting & GIT_SORT_REVERSE);
+			git_revwalk_sorting(walk, sorting);
+		} else if (!strcmp(opts[i], "--reverse")) {
+			sorting = (sorting & ~GIT_SORT_REVERSE)
+			    | ((sorting & GIT_SORT_REVERSE) ? 0 : GIT_SORT_REVERSE);
+			git_revwalk_sorting(walk, sorting);
+		} else if (!strcmp(opts[i], "--not")) {
+			hide = !hide;
+		} else if (opts[i][0] == '^') {
+			if ((error = push_spec(repo, walk, opts[i] + 1, !hide)))
+				return error;
+		} else if (strstr(opts[i], "..")) {
+			if ((error = push_range(repo, walk, opts[i], hide)))
+				return error;
+		} else {
+			if ((error = push_spec(repo, walk, opts[i], hide)))
+				return error;
+		}
+	}
+
+	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;
+}
+
diff --git a/examples/test/test-rev-list.sh b/examples/test/test-rev-list.sh
new file mode 100755
index 0000000..bc0eea7
--- /dev/null
+++ b/examples/test/test-rev-list.sh
@@ -0,0 +1,95 @@
+#!/bin/bash
+
+THIS_FILE="$(readlink -f "$0")"
+ROOT="$(dirname "$(dirname "$(dirname "$THIS_FILE")")")"
+PROGRAM="$ROOT"/examples/rev-list
+LIBDIR="$ROOT"/build
+REPO="$ROOT"/tests-clar/resources/testrepo.git
+
+cd "$REPO"
+
+run () {
+    LD_LIBRARY_PATH="$LIBDIR" "$PROGRAM" "$@"
+}
+
+diff -u - <(run --date-order a4a7dce) <<EOF
+a4a7dce85cf63874e984719f4fdd239f5145052f
+c47800c7266a2be04c571c04d5a6614691ea99bd
+9fd738e8f7967c078dceed8190330fc8648ee56a
+4a202b346bb0fb0db7eff3cffeb3c70babbd2045
+5b5b025afb0b4c913b4c338a42934a3863bf3644
+8496071c1b46c854b31185ea97743be6a8774479
+EOF
+
+out="$(run --topo-order a4a7dce)"
+diff -q - <(echo -n "$out") <<EOF >/dev/null ||
+a4a7dce85cf63874e984719f4fdd239f5145052f
+c47800c7266a2be04c571c04d5a6614691ea99bd
+9fd738e8f7967c078dceed8190330fc8648ee56a
+4a202b346bb0fb0db7eff3cffeb3c70babbd2045
+5b5b025afb0b4c913b4c338a42934a3863bf3644
+8496071c1b46c854b31185ea97743be6a8774479
+EOF
+diff -u - <(echo "$out") <<EOF
+a4a7dce85cf63874e984719f4fdd239f5145052f
+9fd738e8f7967c078dceed8190330fc8648ee56a
+4a202b346bb0fb0db7eff3cffeb3c70babbd2045
+c47800c7266a2be04c571c04d5a6614691ea99bd
+5b5b025afb0b4c913b4c338a42934a3863bf3644
+8496071c1b46c854b31185ea97743be6a8774479
+EOF
+
+diff -u - <(run --date-order --reverse a4a7dce) <<EOF
+8496071c1b46c854b31185ea97743be6a8774479
+5b5b025afb0b4c913b4c338a42934a3863bf3644
+4a202b346bb0fb0db7eff3cffeb3c70babbd2045
+9fd738e8f7967c078dceed8190330fc8648ee56a
+c47800c7266a2be04c571c04d5a6614691ea99bd
+a4a7dce85cf63874e984719f4fdd239f5145052f
+EOF
+
+out=$(run --topo-order --reverse a4a7dce)
+diff -q - <(echo -n "$out") <<EOF >/dev/null ||
+8496071c1b46c854b31185ea97743be6a8774479
+5b5b025afb0b4c913b4c338a42934a3863bf3644
+4a202b346bb0fb0db7eff3cffeb3c70babbd2045
+9fd738e8f7967c078dceed8190330fc8648ee56a
+c47800c7266a2be04c571c04d5a6614691ea99bd
+a4a7dce85cf63874e984719f4fdd239f5145052f
+EOF
+diff -u - <(echo "$out") <<EOF
+8496071c1b46c854b31185ea97743be6a8774479
+5b5b025afb0b4c913b4c338a42934a3863bf3644
+c47800c7266a2be04c571c04d5a6614691ea99bd
+4a202b346bb0fb0db7eff3cffeb3c70babbd2045
+9fd738e8f7967c078dceed8190330fc8648ee56a
+a4a7dce85cf63874e984719f4fdd239f5145052f
+EOF
+
+out="$(run --date-order --topo-order --reverse --reverse a4a7dce)"
+diff -q - <(echo -n "$out") <<EOF >/dev/null ||
+a4a7dce85cf63874e984719f4fdd239f5145052f
+c47800c7266a2be04c571c04d5a6614691ea99bd
+9fd738e8f7967c078dceed8190330fc8648ee56a
+4a202b346bb0fb0db7eff3cffeb3c70babbd2045
+5b5b025afb0b4c913b4c338a42934a3863bf3644
+8496071c1b46c854b31185ea97743be6a8774479
+EOF
+diff -u - <(echo "$out") <<EOF
+a4a7dce85cf63874e984719f4fdd239f5145052f
+9fd738e8f7967c078dceed8190330fc8648ee56a
+4a202b346bb0fb0db7eff3cffeb3c70babbd2045
+c47800c7266a2be04c571c04d5a6614691ea99bd
+5b5b025afb0b4c913b4c338a42934a3863bf3644
+8496071c1b46c854b31185ea97743be6a8774479
+EOF
+
+diff -u - <(run ^9fd738e~2 9fd738e) <<EOF
+9fd738e8f7967c078dceed8190330fc8648ee56a
+4a202b346bb0fb0db7eff3cffeb3c70babbd2045
+EOF
+
+diff -u - <(run --not 9fd738e..9fd738e~2) <<EOF
+9fd738e8f7967c078dceed8190330fc8648ee56a
+4a202b346bb0fb0db7eff3cffeb3c70babbd2045
+EOF
diff --git a/include/git2/revparse.h b/include/git2/revparse.h
index 6edb776..edd8b3c 100644
--- a/include/git2/revparse.h
+++ b/include/git2/revparse.h
@@ -32,6 +32,19 @@ GIT_BEGIN_DECL
  */
 GIT_EXTERN(int) git_revparse_single(git_object **out, git_repository *repo, const char *spec);
 
+/**
+ * Parse a string with the form of a revision range, as accepted by
+ * `git rev-list`, `git diff`, and others.
+ *
+ * @param left (output) the left-hand commit
+ * @param right (output) the right-hand commit
+ * @param threedots (output) 0 if the endpoints are separated by two dots, 1 if by three
+ * @param repo the repository to find the commits in
+ * @param rangelike the rangelike string to be parsed
+ * @return 0 on success, or any error `git_revparse_single` can return
+ */
+GIT_EXTERN(int) git_revparse_rangelike(git_object **left, git_object **right, int *threedots, git_repository *repo, const char *rangelike);
+
 /** @} */
 GIT_END_DECL
 #endif
diff --git a/include/git2/revwalk.h b/include/git2/revwalk.h
index ad57b62..8bfe0b5 100644
--- a/include/git2/revwalk.h
+++ b/include/git2/revwalk.h
@@ -92,7 +92,7 @@ GIT_EXTERN(void) git_revwalk_reset(git_revwalk *walker);
  *
  * The given commit will be used as one of the roots
  * when starting the revision walk. At least one commit
- * must be pushed the repository before a walk can
+ * must be pushed onto the walker before a walk can
  * be started.
  *
  * @param walk the walker being used for the traversal.
@@ -217,6 +217,21 @@ GIT_EXTERN(int) git_revwalk_next(git_oid *out, git_revwalk *walk);
 GIT_EXTERN(void) git_revwalk_sorting(git_revwalk *walk, unsigned int sort_mode);
 
 /**
+ * Push and hide the respective endpoints of the given range.
+ *
+ * The range should be of the form
+ *   <commit>..<commit>
+ * where each <commit> is in the form accepted by 'git_revparse_single'.
+ * The left-hand commit will be hidden and the right-hand commit pushed.
+ *
+ * @param walk the walker being used for the traversal
+ * @param range the range
+ * @return 0 or an error code
+ *
+ */
+GIT_EXTERN(int) git_revwalk_push_range(git_revwalk *walk, const char *range);
+
+/**
  * Free a revision walker previously allocated.
  *
  * @param walk traversal handle to close. If NULL nothing occurs.
diff --git a/src/revparse.c b/src/revparse.c
index 1518a7c..2ba2938 100644
--- a/src/revparse.c
+++ b/src/revparse.c
@@ -867,3 +867,28 @@ cleanup:
 	git_buf_free(&buf);
 	return error;
 }
+
+int git_revparse_rangelike(git_object **left, git_object **right, int *threedots, git_repository *repo, const char *rangelike)
+{
+	int error = 0;
+	const char *p, *q;
+	char *revspec;
+
+	p = strstr(rangelike, "..");
+	if (!p) {
+		giterr_set(GITERR_INVALID, "Malformed range (or rangelike syntax): %s", rangelike);
+		return GIT_EINVALIDSPEC;
+	} else if (p[2] == '.') {
+		*threedots = 1;
+		q = p + 3;
+	} else {
+		*threedots = 0;
+		q = p + 2;
+	}
+
+	revspec = git__substrdup(rangelike, p - rangelike);
+	error = (git_revparse_single(left, repo, revspec)
+	      || git_revparse_single(right, repo, q));
+	git__free(revspec);
+	return error;
+}
diff --git a/src/revwalk.c b/src/revwalk.c
index 02834ab..c107184 100644
--- a/src/revwalk.c
+++ b/src/revwalk.c
@@ -11,6 +11,7 @@
 #include "pool.h"
 
 #include "revwalk.h"
+#include "git2/revparse.h"
 #include "merge.h"
 
 #include <regex.h>
@@ -228,6 +229,30 @@ int git_revwalk_push_ref(git_revwalk *walk, const char *refname)
 	return push_ref(walk, refname, 0);
 }
 
+int git_revwalk_push_range(git_revwalk *walk, const char *range)
+{
+	git_object *left, *right;
+	int threedots;
+	int error = 0;
+
+	if ((error = git_revparse_rangelike(&left, &right, &threedots, walk->repo, range)))
+		return error;
+	if (threedots) {
+		/* TODO: support "<commit>...<commit>" */
+		giterr_set(GITERR_INVALID, "Symmetric differences not implemented in revwalk");
+		return GIT_EINVALIDSPEC;
+	}
+
+	if ((error = push_commit(walk, git_object_id(left), 1)))
+		goto out;
+	error = push_commit(walk, git_object_id(right), 0);
+
+  out:
+	git_object_free(left);
+	git_object_free(right);
+	return error;
+}
+
 int git_revwalk_hide_ref(git_revwalk *walk, const char *refname)
 {
 	assert(walk && refname);
diff --git a/tests-clar/refs/revparse.c b/tests-clar/refs/revparse.c
index e0bccf4..705014c 100644
--- a/tests-clar/refs/revparse.c
+++ b/tests-clar/refs/revparse.c
@@ -32,6 +32,33 @@ static void test_object(const char *spec, const char *expected_oid)
 	test_object_inrepo(spec, expected_oid, g_repo);
 }
 
+static void test_rangelike(const char *rangelike,
+						   const char *expected_left,
+						   const char *expected_right,
+						   int expected_threedots)
+{
+	char objstr[64] = {0};
+	git_object *left, *right;
+	int threedots;
+	int error;
+
+	error = git_revparse_rangelike(&left, &right, &threedots, g_repo, rangelike);
+
+	if (expected_left != NULL) {
+		cl_assert_equal_i(0, error);
+		cl_assert_equal_i(threedots, expected_threedots);
+		git_oid_fmt(objstr, git_object_id(left));
+		cl_assert_equal_s(objstr, expected_left);
+		git_oid_fmt(objstr, git_object_id(right));
+		cl_assert_equal_s(objstr, expected_right);
+	} else
+		cl_assert(error != 0);
+
+	git_object_free(left);
+	git_object_free(right);
+}
+
+
 void test_refs_revparse__initialize(void)
 {
 	cl_git_pass(git_repository_open(&g_repo, cl_fixture("testrepo.git")));
@@ -596,3 +623,19 @@ void test_refs_revparse__try_to_retrieve_branch_before_abbrev_sha(void)
 	git_object_free(target);
 	cl_git_sandbox_cleanup();
 }
+
+
+void test_refs_revparse__range(void)
+{
+	test_rangelike("be3563a^1..be3563a",
+	               "9fd738e8f7967c078dceed8190330fc8648ee56a",
+	               "be3563ae3f795b2b4353bcce3a527ad0a4f7f644",
+	               0);
+
+	test_rangelike("be3563a^1...be3563a",
+	               "9fd738e8f7967c078dceed8190330fc8648ee56a",
+	               "be3563ae3f795b2b4353bcce3a527ad0a4f7f644",
+	               1);
+
+	test_rangelike("be3563a^1.be3563a", NULL, NULL, 0);
+}
diff --git a/tests-clar/revwalk/basic.c b/tests-clar/revwalk/basic.c
index 438ec01..e827762 100644
--- a/tests-clar/revwalk/basic.c
+++ b/tests-clar/revwalk/basic.c
@@ -1,15 +1,14 @@
 #include "clar_libgit2.h"
 
 /*
-	$ git log --oneline --graph --decorate
-	*   a4a7dce (HEAD, br2) Merge branch 'master' into br2
+	*   a4a7dce [0] Merge branch 'master' into br2
 	|\
-	| * 9fd738e (master) a fourth commit
-	| * 4a202b3 a third commit
-	* | c47800c branch commit one
+	| * 9fd738e [1] a fourth commit
+	| * 4a202b3 [2] a third commit
+	* | c47800c [3] branch commit one
 	|/
-	* 5b5b025 another commit
-	* 8496071 testing
+	* 5b5b025 [5] another commit
+	* 8496071 [4] testing
 */
 static const char *commit_head = "a4a7dce85cf63874e984719f4fdd239f5145052f";
 
@@ -39,6 +38,10 @@ static const int commit_sorting_time_reverse[][6] = {
 	{4, 5, 2, 1, 3, 0}
 };
 
+static const int commit_sorting_segment[][6] = {
+	{1, 2, -1, -1, -1, -1}
+};
+
 #define commit_count 6
 static const int result_bytes = 24;
 
@@ -57,22 +60,17 @@ static int get_commit_index(git_oid *raw_oid)
 	return -1;
 }
 
-static int test_walk(git_revwalk *walk, const git_oid *root,
-		int flags, const int possible_results[][6], int results_count)
+static int test_walk_only(git_revwalk *walk,
+		const int possible_results[][commit_count], int results_count)
 {
 	git_oid oid;
-
 	int i;
 	int result_array[commit_count];
 
-	git_revwalk_sorting(walk, flags);
-	git_revwalk_push(walk, root);
-
 	for (i = 0; i < commit_count; ++i)
 		result_array[i] = -1;
 
 	i = 0;
-
 	while (git_revwalk_next(&oid, walk) == 0) {
 		result_array[i++] = get_commit_index(&oid);
 		/*{
@@ -91,6 +89,15 @@ static int test_walk(git_revwalk *walk, const git_oid *root,
 	return GIT_ERROR;
 }
 
+static int test_walk(git_revwalk *walk, const git_oid *root,
+		int flags, const int possible_results[][6], int results_count)
+{
+	git_revwalk_sorting(walk, flags);
+	git_revwalk_push(walk, root);
+
+	return test_walk_only(walk, possible_results, results_count);
+}
+
 static git_repository *_repo;
 static git_revwalk *_walk;
 
@@ -189,3 +196,11 @@ void test_revwalk_basic__disallow_non_commit(void)
 	cl_git_pass(git_oid_fromstr(&oid, "521d87c1ec3aef9824daf6d96cc0ae3710766d91"));
 	cl_git_fail(git_revwalk_push(_walk, &oid));
 }
+
+void test_revwalk_basic__push_range(void)
+{
+	git_revwalk_reset(_walk);
+	git_revwalk_sorting(_walk, 0);
+	cl_git_pass(git_revwalk_push_range(_walk, "9fd738e~2..9fd738e"));
+	cl_git_pass(test_walk_only(_walk, commit_sorting_segment, 1));
+}