status: get blob object id of file on disk

Add git_status_hashfile() to get blob's object id for a file without adding
it to the object database or needing a repository at all.
This functionality is similar to `git hash-object` without '-w'.

include/git2/status.h

+/*
+ * This file is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License, version 2,
+ * as published by the Free Software Foundation.
+ *
+ * In addition to the permissions in the GNU General Public License,
+ * the authors give you unlimited permission to link the compiled
+ * version of this file into combinations with other programs,
+ * and to distribute those combinations without any restriction
+ * coming from the use of this file.  (The General Public License
+ * restrictions do apply in other respects; for example, they cover
+ * modification of the file, and distribution when not linked into
+ * a combined executable.)
+ *
+ * This file is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; see the file COPYING.  If not, write to
+ * the Free Software Foundation, 51 Franklin Street, Fifth Floor,
+ * Boston, MA 02110-1301, USA.
+ */
+#ifndef INCLUDE_git_status_h__
+#define INCLUDE_git_status_h__
+
+#include "common.h"
+#include "types.h"
+
+/**
+ * @file git2/status.h
+ * @brief Git file status routines
+ * @defgroup git_status Git file status routines
+ * @ingroup Git
+ * @{
+ */
+GIT_BEGIN_DECL
+
+/**
+ * Read a file from disk and fill a git_oid with the object id
+ * that the file would have if it were written to the Object
+ * Database as a loose blob. Similar functionality to git.git's
+ * `git hash-object` without the `-w` flag.
+ *
+ * @param out oid structure the result is written into.
+ * @param path file to read and determine object id for
+ * @return GIT_SUCCESS if valid; error code otherwise
+ */
+GIT_EXTERN(int) git_status_hashfile(git_oid *out, const char *path);
+
+/** @} */
+GIT_END_DECL
+#endif

src/status.c

+/*
+ * This file is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License, version 2,
+ * as published by the Free Software Foundation.
+ *
+ * In addition to the permissions in the GNU General Public License,
+ * the authors give you unlimited permission to link the compiled
+ * version of this file into combinations with other programs,
+ * and to distribute those combinations without any restriction
+ * coming from the use of this file.  (The General Public License
+ * restrictions do apply in other respects; for example, they cover
+ * modification of the file, and distribution when not linked into
+ * a combined executable.)
+ *
+ * This file is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; see the file COPYING.  If not, write to
+ * the Free Software Foundation, 51 Franklin Street, Fifth Floor,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#include "common.h"
+#include "git2.h"
+#include "fileops.h"
+#include "hash.h"
+
+int git_status_hashfile(git_oid *out, const char *path)
+{
+	int fd, len;
+	char hdr[64], buffer[2048];
+	git_off_t size;
+	git_hash_ctx *ctx;
+
+	if ((fd = p_open(path, O_RDONLY)) < 0)
+		return git__throw(GIT_ENOTFOUND, "Could not open '%s'", path);
+
+	if ((size = git_futils_filesize(fd)) < 0 || !git__is_sizet(size)) {
+		p_close(fd);
+		return git__throw(GIT_EOSERR, "'%s' appears to be corrupted", path);
+	}
+
+	ctx = git_hash_new_ctx();
+
+	len = snprintf(hdr, sizeof(hdr), "blob %"PRIuZ, (size_t)size);
+	assert(len > 0);
+	assert(((size_t) len) < sizeof(hdr));
+	if (len < 0 || ((size_t) len) >= sizeof(hdr))
+		return git__throw(GIT_ERROR, "Failed to format blob header. Length is out of bounds");
+
+	git_hash_update(ctx, hdr, len+1);
+
+	while (size > 0) {
+		ssize_t read_len;
+
+		read_len = read(fd, buffer, sizeof(buffer));
+
+		if (read_len < 0) {
+			p_close(fd);
+			git_hash_free_ctx(ctx);
+			return git__throw(GIT_EOSERR, "Can't read full file '%s'", path);
+		}
+
+		git_hash_update(ctx, buffer, read_len);
+		size -= read_len;
+	}
+
+	p_close(fd);
+
+	git_hash_final(out, ctx);
+	git_hash_free_ctx(ctx);
+
+	return GIT_SUCCESS;
+}

tests/NAMING

@@ -48,3 +48,5 @@ Categories
 16__: Remotes
 
 17__: Buffers
+
+18__: File Status

tests/resources/status/test.txt

+test

tests/t18-status.c

+/*
+ * This file is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License, version 2,
+ * as published by the Free Software Foundation.
+ *
+ * In addition to the permissions in the GNU General Public License,
+ * the authors give you unlimited permission to link the compiled
+ * version of this file into combinations with other programs,
+ * and to distribute those combinations without any restriction
+ * coming from the use of this file.  (The General Public License
+ * restrictions do apply in other respects; for example, they cover
+ * modification of the file, and distribution when not linked into
+ * a combined executable.)
+ *
+ * This file is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; see the file COPYING.  If not, write to
+ * the Free Software Foundation, 51 Franklin Street, Fifth Floor,
+ * Boston, MA 02110-1301, USA.
+ */
+#include "test_lib.h"
+#include "test_helpers.h"
+#include "fileops.h"
+#include "git2/status.h"
+
+#define STATUS_FOLDER TEST_RESOURCES "/status/"
+#define TEMP_STATUS_FOLDER TEMP_FOLDER "status"
+
+static const char *test_blob_oid = "9daeafb9864cf43055ae93beb0afd6c7d144bfa4";
+
+BEGIN_TEST(file0, "test retrieving OID from a file apart from the ODB")
+	char current_workdir[GIT_PATH_MAX];
+	char path_statusfiles[GIT_PATH_MAX];
+	char temp_path[GIT_PATH_MAX];
+	git_oid expected_id, actual_id;
+
+	must_pass(p_getcwd(current_workdir, sizeof(current_workdir)));
+	strcpy(path_statusfiles, current_workdir);
+	git_path_join(path_statusfiles, path_statusfiles, TEMP_STATUS_FOLDER);
+
+	must_pass(copydir_recurs(STATUS_FOLDER, path_statusfiles));
+	git_path_join(temp_path, path_statusfiles, "test.txt");
+
+	must_pass(git_futils_exists(temp_path));
+
+	git_oid_fromstr(&expected_id, test_blob_oid);
+	must_pass(git_status_hashfile(&actual_id, temp_path));
+
+	must_be_true(git_oid_cmp(&expected_id, &actual_id) == 0);
+
+	git_futils_rmdir_r(TEMP_STATUS_FOLDER, 1);
+END_TEST
+
+BEGIN_SUITE(status)
+	ADD_TEST(file0);
+END_SUITE

tests/test_main.c

@@ -45,6 +45,7 @@ DECLARE_SUITE(threads);
 DECLARE_SUITE(config);
 DECLARE_SUITE(remotes);
 DECLARE_SUITE(buffers);
+DECLARE_SUITE(status);
 
 static libgit2_suite suite_methods[]= {
 	SUITE_NAME(core),
@@ -63,6 +64,7 @@ static libgit2_suite suite_methods[]= {
 	SUITE_NAME(config),
 	SUITE_NAME(remotes),
 	SUITE_NAME(buffers),
+	SUITE_NAME(status),
 };
 
 #define GIT_SUITE_COUNT (ARRAY_SIZE(suite_methods))