thodg/libgit2

diff --git a/cmake/Modules/FindPCRE2.cmake b/cmake/Modules/FindPCRE2.cmake
index 122f0e9..f8c5639 100644
--- a/cmake/Modules/FindPCRE2.cmake
+++ b/cmake/Modules/FindPCRE2.cmake
@@ -20,15 +20,14 @@ FIND_PATH(PCRE2_INCLUDE_DIR NAMES pcre2posix.h)
 
 # Look for the library.
 FIND_LIBRARY(PCRE2_LIBRARY NAMES pcre2-8)
-FIND_LIBRARY(PCRE2_POSIX_LIBRARY NAMES pcre2-posix)
 
 # Handle the QUIETLY and REQUIRED arguments and set PCRE2_FOUND to TRUE if all listed variables are TRUE.
 INCLUDE(FindPackageHandleStandardArgs)
-FIND_PACKAGE_HANDLE_STANDARD_ARGS(PCRE2 DEFAULT_MSG PCRE2_LIBRARY PCRE2_POSIX_LIBRARY PCRE2_INCLUDE_DIR)
+FIND_PACKAGE_HANDLE_STANDARD_ARGS(PCRE2 DEFAULT_MSG PCRE2_LIBRARY PCRE2_INCLUDE_DIR)
 
 # Copy the results to the output variables.
 IF(PCRE2_FOUND)
-	SET(PCRE2_LIBRARIES ${PCRE2_LIBRARY} ${PCRE2_POSIX_LIBRARY})
+	SET(PCRE2_LIBRARIES ${PCRE2_LIBRARY})
 	SET(PCRE2_INCLUDE_DIRS ${PCRE2_INCLUDE_DIR})
 ELSE(PCRE2_FOUND)
 	SET(PCRE2_LIBRARIES)
diff --git a/src/common.h b/src/common.h
index 8a5761a..a4152ca 100644
--- a/src/common.h
+++ b/src/common.h
@@ -88,7 +88,6 @@
 #include "git2/deprecated.h"
 
 #include "posix.h"
-#include "posix_regex.h"
 
 #define DEFAULT_BUFSIZE 65536
 #define FILEIO_BUFSIZE DEFAULT_BUFSIZE
diff --git a/src/config.c b/src/config.c
index d0e439b..8338da0 100644
--- a/src/config.c
+++ b/src/config.c
@@ -7,13 +7,15 @@
 
 #include "config.h"
 
-#include "sysdir.h"
 #include "git2/config.h"
 #include "git2/sys/config.h"
-#include "vector.h"
+
 #include "buf_text.h"
 #include "config_backend.h"
+#include "regexp.h"
+#include "sysdir.h"
 #include "transaction.h"
+#include "vector.h"
 #if GIT_WIN32
 # include <windows.h>
 #endif
@@ -345,7 +347,7 @@ typedef struct {
 	git_config_iterator parent;
 	git_config_iterator *current;
 	const git_config *cfg;
-	p_regex_t regex;
+	git_regexp regex;
 	size_t i;
 } all_iter;
 
@@ -423,7 +425,7 @@ static int all_iter_glob_next(git_config_entry **entry, git_config_iterator *_it
 	 */
 	while ((error = all_iter_next(entry, _iter)) == 0) {
 		/* skip non-matching keys if regexp was provided */
-		if (p_regexec(&iter->regex, (*entry)->name, 0, NULL, 0) != 0)
+		if (git_regexp_match(&iter->regex, (*entry)->name) != 0)
 			continue;
 
 		/* and simply return if we like the entry's name */
@@ -447,7 +449,7 @@ static void all_iter_glob_free(git_config_iterator *_iter)
 {
 	all_iter *iter = (all_iter *) _iter;
 
-	p_regfree(&iter->regex);
+	git_regexp_dispose(&iter->regex);
 	all_iter_free(_iter);
 }
 
@@ -480,8 +482,7 @@ int git_config_iterator_glob_new(git_config_iterator **out, const git_config *cf
 	iter = git__calloc(1, sizeof(all_iter));
 	GIT_ERROR_CHECK_ALLOC(iter);
 
-	if ((result = p_regcomp(&iter->regex, regexp, P_REG_EXTENDED)) != 0) {
-		git_error_set_regex(&iter->regex, result);
+	if ((result = git_regexp_compile(&iter->regex, regexp, 0)) < 0) {
 		git__free(iter);
 		return -1;
 	}
@@ -510,18 +511,13 @@ int git_config_backend_foreach_match(
 {
 	git_config_entry *entry;
 	git_config_iterator* iter;
-	p_regex_t regex;
+	git_regexp regex;
 	int error = 0;
 
 	assert(backend && cb);
 
-	if (regexp != NULL) {
-		if ((error = p_regcomp(&regex, regexp, P_REG_EXTENDED)) != 0) {
-			git_error_set_regex(&regex, error);
-			p_regfree(&regex);
-			return -1;
-		}
-	}
+	if (regexp && git_regexp_compile(&regex, regexp, 0) < 0)
+		return -1;
 
 	if ((error = backend->iterator(&iter, backend)) < 0) {
 		iter = NULL;
@@ -530,7 +526,7 @@ int git_config_backend_foreach_match(
 
 	while (!(iter->next(&entry, iter) < 0)) {
 		/* skip non-matching keys if regexp was provided */
-		if (regexp && p_regexec(&regex, entry->name, 0, NULL, 0) != 0)
+		if (regexp && git_regexp_match(&regex, entry->name) != 0)
 			continue;
 
 		/* abort iterator on non-zero return value */
@@ -541,7 +537,7 @@ int git_config_backend_foreach_match(
 	}
 
 	if (regexp != NULL)
-		p_regfree(&regex);
+		git_regexp_dispose(&regex);
 
 	iter->free(iter);
 
@@ -981,7 +977,7 @@ typedef struct {
 	git_config_iterator parent;
 	git_config_iterator *iter;
 	char *name;
-	p_regex_t regex;
+	git_regexp regex;
 	int have_regex;
 } multivar_iter;
 
@@ -997,7 +993,7 @@ static int multivar_iter_next(git_config_entry **entry, git_config_iterator *_it
 		if (!iter->have_regex)
 			return 0;
 
-		if (p_regexec(&iter->regex, (*entry)->value, 0, NULL, 0) == 0)
+		if (git_regexp_match(&iter->regex, (*entry)->value) == 0)
 			return 0;
 	}
 
@@ -1012,7 +1008,7 @@ void multivar_iter_free(git_config_iterator *_iter)
 
 	git__free(iter->name);
 	if (iter->have_regex)
-		p_regfree(&iter->regex);
+		git_regexp_dispose(&iter->regex);
 	git__free(iter);
 }
 
@@ -1032,13 +1028,8 @@ int git_config_multivar_iterator_new(git_config_iterator **out, const git_config
 		goto on_error;
 
 	if (regexp != NULL) {
-		error = p_regcomp(&iter->regex, regexp, P_REG_EXTENDED);
-		if (error != 0) {
-			git_error_set_regex(&iter->regex, error);
-			error = -1;
-			p_regfree(&iter->regex);
+		if ((error = git_regexp_compile(&iter->regex, regexp, 0)) < 0)
 			goto on_error;
-		}
 
 		iter->have_regex = 1;
 	}
diff --git a/src/config_file.c b/src/config_file.c
index 849096d..bf770c9 100644
--- a/src/config_file.c
+++ b/src/config_file.c
@@ -18,6 +18,7 @@
 #include "config_entries.h"
 #include "config_parse.h"
 #include "filebuf.h"
+#include "regexp.h"
 #include "strmap.h"
 #include "sysdir.h"
 #include "wildmatch.h"
@@ -61,7 +62,7 @@ typedef struct {
 
 static int config_read(git_config_entries *entries, const git_repository *repo, config_file *file, git_config_level_t level, int depth);
 static int config_read_buffer(git_config_entries *entries, const git_repository *repo, config_file *file, git_config_level_t level, int depth, const char *buf, size_t buflen);
-static int config_write(config_file_backend *cfg, const char *orig_key, const char *key, const p_regex_t *preg, const char *value);
+static int config_write(config_file_backend *cfg, const char *orig_key, const char *key, const git_regexp *preg, const char *value);
 static char *escape_value(const char *ptr);
 
 /**
@@ -350,21 +351,17 @@ static int config_set_multivar(
 	git_config_backend *cfg, const char *name, const char *regexp, const char *value)
 {
 	config_file_backend *b = GIT_CONTAINER_OF(cfg, config_file_backend, parent);
-	char *key;
-	p_regex_t preg;
+	git_regexp preg;
 	int result;
+	char *key;
 
 	assert(regexp);
 
 	if ((result = git_config__normalize_name(name, &key)) < 0)
 		return result;
 
-	result = p_regcomp(&preg, regexp, P_REG_EXTENDED);
-	if (result != 0) {
-		git_error_set_regex(&preg, result);
-		result = -1;
+	if ((result = git_regexp_compile(&preg, regexp, 0)) < 0)
 		goto out;
-	}
 
 	/* If we do have it, set call config_write() and reload */
 	if ((result = config_write(b, name, key, &preg, value)) < 0)
@@ -372,7 +369,7 @@ static int config_set_multivar(
 
 out:
 	git__free(key);
-	p_regfree(&preg);
+	git_regexp_dispose(&preg);
 
 	return result;
 }
@@ -412,7 +409,7 @@ static int config_delete_multivar(git_config_backend *cfg, const char *name, con
 	config_file_backend *b = GIT_CONTAINER_OF(cfg, config_file_backend, parent);
 	git_config_entries *entries = NULL;
 	git_config_entry *entry = NULL;
-	p_regex_t preg = { 0 };
+	git_regexp preg = GIT_REGEX_INIT;
 	char *key = NULL;
 	int result;
 
@@ -430,11 +427,8 @@ static int config_delete_multivar(git_config_backend *cfg, const char *name, con
 		goto out;
 	}
 
-	if ((result = p_regcomp(&preg, regexp, P_REG_EXTENDED)) != 0) {
-		git_error_set_regex(&preg, result);
-		result = -1;
+	if ((result = git_regexp_compile(&preg, regexp, 0)) < 0)
 		goto out;
-	}
 
 	if ((result = config_write(b, name, key, &preg, NULL)) < 0)
 		goto out;
@@ -442,7 +436,7 @@ static int config_delete_multivar(git_config_backend *cfg, const char *name, con
 out:
 	git_config_entries_free(entries);
 	git__free(key);
-	p_regfree(&preg);
+	git_regexp_dispose(&preg);
 	return result;
 }
 
@@ -928,7 +922,7 @@ struct write_data {
 	const char *section;
 	const char *orig_name;
 	const char *name;
-	const p_regex_t *preg;
+	const git_regexp *preg;
 	const char *value;
 };
 
@@ -1033,7 +1027,7 @@ static int write_on_variable(
 
 	/* If we have a regex to match the value, see if it matches */
 	if (has_matched && write_data->preg != NULL)
-		has_matched = (p_regexec(write_data->preg, var_value, 0, NULL, 0) == 0);
+		has_matched = (git_regexp_match(write_data->preg, var_value) == 0);
 
 	/* If this isn't the name/value we're looking for, simply dump the
 	 * existing data back out and continue on.
@@ -1094,7 +1088,8 @@ static int write_on_eof(
 /*
  * This is pretty much the parsing, except we write out anything we don't have
  */
-static int config_write(config_file_backend *cfg, const char *orig_key, const char *key, const p_regex_t *preg, const char* value)
+static int config_write(config_file_backend *cfg, const char *orig_key, const char *key, const git_regexp *preg, const char* value)
+
 {
 	char *orig_section = NULL, *section = NULL, *orig_name, *name, *ldot;
 	git_buf buf = GIT_BUF_INIT, contents = GIT_BUF_INIT;
diff --git a/src/diff_driver.c b/src/diff_driver.c
index 6919e4e..831d326 100644
--- a/src/diff_driver.c
+++ b/src/diff_driver.c
@@ -15,6 +15,7 @@
 #include "map.h"
 #include "buf_text.h"
 #include "config.h"
+#include "regexp.h"
 #include "repository.h"
 
 typedef enum {
@@ -25,7 +26,7 @@ typedef enum {
 } git_diff_driver_t;
 
 typedef struct {
-	p_regex_t re;
+	git_regexp re;
 	int flags;
 } git_diff_driver_pattern;
 
@@ -39,7 +40,7 @@ struct git_diff_driver {
 	uint32_t binary_flags;
 	uint32_t other_flags;
 	git_array_t(git_diff_driver_pattern) fn_patterns;
-	p_regex_t  word_pattern;
+	git_regexp  word_pattern;
 	char name[GIT_FLEX_ARRAY];
 };
 
@@ -113,7 +114,7 @@ static int diff_driver_add_patterns(
 		if (error < 0)
 			break;
 
-		if ((error = p_regcomp(&pat->re, buf.ptr, regex_flags)) != 0) {
+		if ((error = git_regexp_compile(&pat->re, buf.ptr, regex_flags)) != 0) {
 			/*
 			 * TODO: issue a warning
 			 */
@@ -130,7 +131,7 @@ static int diff_driver_add_patterns(
 
 static int diff_driver_xfuncname(const git_config_entry *entry, void *payload)
 {
-	return diff_driver_add_patterns(payload, entry->value, P_REG_EXTENDED);
+	return diff_driver_add_patterns(payload, entry->value, 0);
 }
 
 static int diff_driver_funcname(const git_config_entry *entry, void *payload)
@@ -205,16 +206,12 @@ static int git_diff_driver_builtin(
 
 	if (ddef->fns &&
 		(error = diff_driver_add_patterns(
-			drv, ddef->fns, ddef->flags | P_REG_EXTENDED)) < 0)
+			drv, ddef->fns, ddef->flags)) < 0)
 		goto done;
 
 	if (ddef->words &&
-		(error = p_regcomp(
-			&drv->word_pattern, ddef->words, ddef->flags | P_REG_EXTENDED)))
-	{
-		error = git_error_set_regex(&drv->word_pattern, error);
+	    (error = git_regexp_compile(&drv->word_pattern, ddef->words, ddef->flags)) < 0)
 		goto done;
-	}
 
 	if ((error = git_strmap_set(reg->drivers, drv->name, drv)) < 0)
 		goto done;
@@ -316,11 +313,10 @@ static int git_diff_driver_load(
 		goto done;
 	if (!ce || !ce->value)
 		/* no diff.<driver>.wordregex, so just continue */;
-	else if (!(error = p_regcomp(&drv->word_pattern, ce->value, P_REG_EXTENDED)))
+	else if (!(error = git_regexp_compile(&drv->word_pattern, ce->value, 0)))
 		found_driver = true;
 	else {
 		/* TODO: warn about bad regex instead of failure */
-		error = git_error_set_regex(&drv->word_pattern, error);
 		goto done;
 	}
 
@@ -400,10 +396,10 @@ void git_diff_driver_free(git_diff_driver *driver)
 		return;
 
 	for (i = 0; i < git_array_size(driver->fn_patterns); ++i)
-		p_regfree(& git_array_get(driver->fn_patterns, i)->re);
+		git_regexp_dispose(& git_array_get(driver->fn_patterns, i)->re);
 	git_array_clear(driver->fn_patterns);
 
-	p_regfree(&driver->word_pattern);
+	git_regexp_dispose(&driver->word_pattern);
 
 	git__free(driver);
 }
@@ -451,19 +447,19 @@ static int diff_context_line__pattern_match(
 	git_diff_driver *driver, git_buf *line)
 {
 	size_t i, maxi = git_array_size(driver->fn_patterns);
-	p_regmatch_t pmatch[2];
+	git_regmatch pmatch[2];
 
 	for (i = 0; i < maxi; ++i) {
 		git_diff_driver_pattern *pat = git_array_get(driver->fn_patterns, i);
 
-		if (!p_regexec(&pat->re, line->ptr, 2, pmatch, 0)) {
+		if (!git_regexp_search(&pat->re, line->ptr, 2, pmatch)) {
 			if (pat->flags & REG_NEGATE)
 				return false;
 
 			/* use pmatch data to trim line data */
-			i = (pmatch[1].rm_so >= 0) ? 1 : 0;
-			git_buf_consume(line, git_buf_cstr(line) + pmatch[i].rm_so);
-			git_buf_truncate(line, pmatch[i].rm_eo - pmatch[i].rm_so);
+			i = (pmatch[1].start >= 0) ? 1 : 0;
+			git_buf_consume(line, git_buf_cstr(line) + pmatch[i].start);
+			git_buf_truncate(line, pmatch[i].end - pmatch[i].start);
 			git_buf_rtrim(line);
 
 			return true;
diff --git a/src/errors.c b/src/errors.c
index 18d6c2d..c75f6b1 100644
--- a/src/errors.c
+++ b/src/errors.c
@@ -110,21 +110,6 @@ void git_error_set_str(int error_class, const char *string)
 		set_error_from_buffer(error_class);
 }
 
-int git_error_set_regex(const p_regex_t *regex, int error_code)
-{
-	char error_buf[1024];
-
-	assert(error_code);
-
-	p_regerror(error_code, regex, error_buf, sizeof(error_buf));
-	git_error_set_str(GIT_ERROR_REGEX, error_buf);
-
-	if (error_code == P_REG_NOMATCH)
-		return GIT_ENOTFOUND;
-
-	return GIT_EINVALIDSPEC;
-}
-
 void git_error_clear(void)
 {
 	if (GIT_GLOBAL->last_error != NULL) {
diff --git a/src/errors.h b/src/errors.h
index 86f06f9..a2f60f7 100644
--- a/src/errors.h
+++ b/src/errors.h
@@ -8,7 +8,6 @@
 #ifndef INCLUDE_errors_h__
 #define INCLUDE_errors_h__
 
-#include "posix_regex.h"
 #include "common.h"
 
 /*
@@ -18,12 +17,6 @@ void git_error_set(int error_class, const char *fmt, ...) GIT_FORMAT_PRINTF(2, 3
 void git_error_vset(int error_class, const char *fmt, va_list ap);
 
 /**
- * Set the error message for a regex failure, using the internal regex
- * error code lookup and return a libgit error code.
- */
-int git_error_set_regex(const p_regex_t *regex, int error_code);
-
-/**
  * Set error message for user callback if needed.
  *
  * If the error code in non-zero and no error message is set, this
diff --git a/src/posix_regex.h b/src/posix_regex.h
deleted file mode 100644
index 421ffeb..0000000
--- a/src/posix_regex.h
+++ /dev/null
@@ -1,73 +0,0 @@
-/*
- * 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.
- */
-#ifndef INCLUDE_posix_regex_h__
-#define INCLUDE_posix_regex_h__
-
-#include "common.h"
-
-/*
- * Regular expressions: if we were asked to use PCRE (either our
- * bundled version or a system version) then use their regcomp
- * compatible implementation.
- */
-
-#ifdef GIT_REGEX_BUILTIN
-
-# include "pcreposix.h"
-
-# define P_REG_EXTENDED PCRE_REG_EXTENDED
-# define P_REG_ICASE PCRE_REG_ICASE
-# define P_REG_NOMATCH PCRE_REG_NOMATCH
-
-# define p_regex_t pcre_regex_t
-# define p_regmatch_t pcre_regmatch_t
-# define p_regcomp pcre_regcomp
-# define p_regerror pcre_regerror
-# define p_regexec pcre_regexec
-# define p_regfree pcre_regfree
-
-/*
- * Use the system-provided `regex` routines, whether that's via the
- * PCRE emulation layer, or libc, preferring `regcomp_l` it's available.
- */
-
-#else
-
-# if defined(GIT_REGEX_PCRE2)
-#  include <pcre2posix.h>
-# elif defined(GIT_REGEX_PCRE)
-#  include <pcreposix.h>
-# else
-#  include <regex.h>
-# endif
-
-# define P_REG_EXTENDED REG_EXTENDED
-# define P_REG_ICASE REG_ICASE
-# define P_REG_NOMATCH REG_NOMATCH
-
-# define p_regex_t regex_t
-# define p_regmatch_t regmatch_t
-
-# define p_regerror regerror
-# define p_regexec regexec
-# define p_regfree regfree
-
-# ifdef GIT_REGEX_REGCOMP_L
-#  include <xlocale.h>
-
-GIT_INLINE(int) p_regcomp(p_regex_t *preg, const char *pattern, int cflags)
-{
-	return regcomp_l(preg, pattern, cflags, (locale_t) 0);
-}
-
-# else
-#  define p_regcomp regcomp
-# endif /* GIT_REGEX_REGCOMP_L */
-
-#endif
-
-#endif
diff --git a/src/regexp.c b/src/regexp.c
new file mode 100644
index 0000000..05ed190
--- /dev/null
+++ b/src/regexp.c
@@ -0,0 +1,221 @@
+/*
+ * 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 "regexp.h"
+
+#if defined(GIT_REGEX_BUILTIN) || defined(GIT_REGEX_PCRE)
+
+int git_regexp_compile(git_regexp *r, const char *pattern, int flags)
+{
+	int erroffset, cflags = 0;
+	const char *error;
+
+	if (flags & GIT_REGEXP_ICASE)
+		cflags |= PCRE_CASELESS;
+
+	if ((*r = pcre_compile(pattern, cflags, &error, &erroffset, NULL)) == NULL) {
+		git_error_set_str(GIT_ERROR_REGEX, error);
+		return GIT_EINVALIDSPEC;
+	}
+
+	return 0;
+}
+
+void git_regexp_dispose(git_regexp *r)
+{
+	pcre_free(*r);
+	*r = NULL;
+}
+
+int git_regexp_match(const git_regexp *r, const char *string)
+{
+	int error;
+	if ((error = pcre_exec(*r, NULL, string, (int) strlen(string), 0, 0, NULL, 0)) < 0)
+		return (error == PCRE_ERROR_NOMATCH) ? GIT_ENOTFOUND : GIT_EINVALIDSPEC;
+	return 0;
+}
+
+int git_regexp_search(const git_regexp *r, const char *string, size_t nmatches, git_regmatch *matches)
+{
+	int static_ovec[9], *ovec;
+	int error;
+	size_t i;
+
+	/* The ovec array always needs to be a mutiple of three */
+	if (nmatches <= ARRAY_SIZE(static_ovec) / 3)
+		ovec = static_ovec;
+	else
+		ovec = git__calloc(nmatches * 3, sizeof(*ovec));
+	GIT_ERROR_CHECK_ALLOC(ovec);
+
+	if ((error = pcre_exec(*r, NULL, string, (int) strlen(string), 0, 0, ovec, (int) nmatches * 3)) < 0)
+		goto out;
+
+	if (error == 0)
+		error = (int) nmatches;
+
+	for (i = 0; i < (unsigned int) error; i++) {
+		matches[i].start = (ovec[i * 2] < 0) ? -1 : ovec[i * 2];
+		matches[i].end = (ovec[i * 2 + 1] < 0) ? -1 : ovec[i * 2 + 1];
+	}
+	for (i = (unsigned int) error; i < nmatches; i++)
+		matches[i].start = matches[i].end = -1;
+
+out:
+	if (nmatches > ARRAY_SIZE(static_ovec) / 3)
+		git__free(ovec);
+	if (error < 0)
+		return (error == PCRE_ERROR_NOMATCH) ? GIT_ENOTFOUND : GIT_EINVALIDSPEC;
+	return 0;
+}
+
+#elif defined(GIT_REGEX_PCRE2)
+
+int git_regexp_compile(git_regexp *r, const char *pattern, int flags)
+{
+	unsigned char errmsg[1024];
+	unsigned long erroff;
+	int error, cflags = 0;
+
+	if (flags & GIT_REGEXP_ICASE)
+		cflags |= PCRE2_CASELESS;
+
+	if ((*r = pcre2_compile((const unsigned char *) pattern, PCRE2_ZERO_TERMINATED,
+				cflags, &error, &erroff, NULL)) == NULL) {
+		pcre2_get_error_message(error, errmsg, sizeof(errmsg));
+		git_error_set_str(GIT_ERROR_REGEX, (char *) errmsg);
+		return GIT_EINVALIDSPEC;
+	}
+
+	return 0;
+}
+
+void git_regexp_dispose(git_regexp *r)
+{
+	pcre2_code_free(*r);
+	*r = NULL;
+}
+
+int git_regexp_match(const git_regexp *r, const char *string)
+{
+	pcre2_match_data *data;
+	int error;
+
+	data = pcre2_match_data_create(1, NULL);
+	GIT_ERROR_CHECK_ALLOC(data);
+
+	if ((error = pcre2_match(*r, (const unsigned char *) string, strlen(string),
+			 0, 0, data, NULL)) < 0)
+		return (error == PCRE2_ERROR_NOMATCH) ? GIT_ENOTFOUND : GIT_EINVALIDSPEC;
+
+	pcre2_match_data_free(data);
+	return 0;
+}
+
+int git_regexp_search(const git_regexp *r, const char *string, size_t nmatches, git_regmatch *matches)
+{
+	pcre2_match_data *data = NULL;
+	PCRE2_SIZE *ovec;
+	int error;
+	size_t i;
+
+	if ((data = pcre2_match_data_create(nmatches, NULL)) == NULL) {
+		git_error_set_oom();
+		goto out;
+	}
+
+	if ((error = pcre2_match(*r, (const unsigned char *) string, strlen(string),
+			     0, 0, data, NULL)) < 0)
+		goto out;
+
+	if (error == 0 || (unsigned int) error  > nmatches)
+		error = nmatches;
+	ovec = pcre2_get_ovector_pointer(data);
+
+	for (i = 0; i < (unsigned int) error; i++) {
+		matches[i].start = (ovec[i * 2] == PCRE2_UNSET) ? -1 : (ssize_t) ovec[i * 2];
+		matches[i].end = (ovec[i * 2 + 1] == PCRE2_UNSET) ? -1 :  (ssize_t) ovec[i * 2 + 1];
+	}
+	for (i = (unsigned int) error; i < nmatches; i++)
+		matches[i].start = matches[i].end = -1;
+
+out:
+	pcre2_match_data_free(data);
+	if (error < 0)
+		return (error == PCRE2_ERROR_NOMATCH) ? GIT_ENOTFOUND : GIT_EINVALIDSPEC;
+	return 0;
+}
+
+#elif defined(GIT_REGEX_REGCOMP) || defined(GIT_REGEX_REGCOMP_L)
+
+#if defined(GIT_REGEX_REGCOMP_L)
+# include <xlocale.h>
+#endif
+
+int git_regexp_compile(git_regexp *r, const char *pattern, int flags)
+{
+	int cflags = REG_EXTENDED, error;
+	char errmsg[1024];
+
+	if (flags & GIT_REGEXP_ICASE)
+		cflags |= REG_ICASE;
+
+# if defined(GIT_REGEX_REGCOMP)
+	if ((error = regcomp(r, pattern, cflags)) != 0)
+# else
+	if ((error = regcomp_l(r, pattern, cflags, (locale_t) 0)) != 0)
+# endif
+	{
+		regerror(error, r, errmsg, sizeof(errmsg));
+		git_error_set_str(GIT_ERROR_REGEX, errmsg);
+		return GIT_EINVALIDSPEC;
+	}
+
+	return 0;
+}
+
+void git_regexp_dispose(git_regexp *r)
+{
+	regfree(r);
+}
+
+int git_regexp_match(const git_regexp *r, const char *string)
+{
+	int error;
+	if ((error = regexec(r, string, 0, NULL, 0)) != 0)
+		return (error == REG_NOMATCH) ? GIT_ENOTFOUND : GIT_EINVALIDSPEC;
+	return 0;
+}
+
+int git_regexp_search(const git_regexp *r, const char *string, size_t nmatches, git_regmatch *matches)
+{
+	regmatch_t static_m[3], *m;
+	int error;
+	size_t i;
+
+	if (nmatches <= ARRAY_SIZE(static_m))
+		m = static_m;
+	else
+		m = git__calloc(nmatches, sizeof(*m));
+
+	if ((error = regexec(r, string, nmatches, m, 0)) != 0)
+		goto out;
+
+	for (i = 0; i < nmatches; i++) {
+		matches[i].start = (m[i].rm_so < 0) ? -1 : m[i].rm_so;
+		matches[i].end = (m[i].rm_eo < 0) ? -1 : m[i].rm_eo;
+	}
+
+out:
+	if (nmatches > ARRAY_SIZE(static_m))
+		git__free(m);
+	if (error)
+		return (error == REG_NOMATCH) ? GIT_ENOTFOUND : GIT_EINVALIDSPEC;
+	return 0;
+}
+
+#endif
diff --git a/src/regexp.h b/src/regexp.h
new file mode 100644
index 0000000..2592ef3
--- /dev/null
+++ b/src/regexp.h
@@ -0,0 +1,97 @@
+/*
+ * 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.
+ */
+
+#ifndef INCLUDE_regexp_h__
+#define INCLUDE_regexp_h__
+
+#include "common.h"
+
+#if defined(GIT_REGEX_BUILTIN) || defined(GIT_REGEX_PCRE)
+# include "pcre.h"
+typedef pcre *git_regexp;
+# define GIT_REGEX_INIT NULL
+#elif defined(GIT_REGEX_PCRE2)
+# define PCRE2_CODE_UNIT_WIDTH 8
+# include <pcre2.h>
+typedef pcre2_code *git_regexp;
+# define GIT_REGEX_INIT NULL
+#elif defined(GIT_REGEX_REGCOMP) || defined(GIT_REGEX_REGCOMP_L)
+# include <regex.h>
+typedef regex_t git_regexp;
+# define GIT_REGEX_INIT { 0 }
+#else
+# error "No regex backend"
+#endif
+
+/** Options supported by @git_regexp_compile. */
+typedef enum {
+	/** Enable case-insensitive matching */
+	GIT_REGEXP_ICASE = (1 << 0)
+} git_regexp_flags_t;
+
+/** Structure containing information about regular expression matching groups */
+typedef struct {
+	/** Start of the given match. -1 if the group didn't match anything */
+	ssize_t start;
+	/** End of the given match. -1 if the group didn't match anything */
+	ssize_t end;
+} git_regmatch;
+
+/**
+ * Compile a regular expression. The compiled expression needs to
+ * be cleaned up afterwards with `git_regexp_dispose`.
+ *
+ * @param r Pointer to the storage where to initialize the regular expression.
+ * @param pattern The pattern that shall be compiled.
+ * @param flags Flags to alter how the pattern shall be handled.
+ *              0 for defaults, otherwise see @git_regexp_flags_t.
+ * @return 0 on success, otherwise a negative return value.
+ */
+int git_regexp_compile(git_regexp *r, const char *pattern, int flags);
+
+/**
+ * Free memory associated with the regular expression
+ *
+ * @param r The regular expression structure to dispose.
+ */
+void git_regexp_dispose(git_regexp *r);
+
+/**
+ * Test whether a given string matches a compiled regular
+ * expression.
+ *
+ * @param r Compiled regular expression.
+ * @param string String to match against the regular expression.
+ * @return 0 if the string matches, a negative error code
+ *         otherwise. GIT_ENOTFOUND if no match was found,
+ *         GIT_EINVALIDSPEC if the regular expression matching
+ *         was invalid.
+ */
+int git_regexp_match(const git_regexp *r, const char *string);
+
+/**
+ * Search for matches inside of a given string.
+ *
+ * Given a regular expression with capturing groups, this
+ * function will populate provided @git_regmatch structures with
+ * offsets for each of the given matches. Non-matching groups
+ * will have start and end values of the respective @git_regmatch
+ * structure set to -1.
+ *
+ * @param r Compiled regular expression.
+ * @param string String to match against the regular expression.
+ * @param nmatches Number of @git_regmatch structures provided by
+ *                 the user.
+ * @param matches Pointer to an array of @git_regmatch structures.
+ * @return 0 if the string matches, a negative error code
+ *         otherwise. GIT_ENOTFOUND if no match was found,
+ *         GIT_EINVALIDSPEC if the regular expression matching
+ *         was invalid.
+ */
+int git_regexp_search(const git_regexp *r, const char *string, size_t nmatches, git_regmatch *matches);
+
+#endif
diff --git a/src/revparse.c b/src/revparse.c
index 4bde0d7..2618b38 100644
--- a/src/revparse.c
+++ b/src/revparse.c
@@ -12,6 +12,7 @@
 #include "buffer.h"
 #include "tree.h"
 #include "refdb.h"
+#include "regexp.h"
 
 #include "git2.h"
 
@@ -42,7 +43,7 @@ static int maybe_abbrev(git_object** out, git_repository *repo, const char *spec
 	return maybe_sha_or_abbrev(out, repo, spec, speclen);
 }
 
-static int build_regex(p_regex_t *regex, const char *pattern)
+static int build_regex(git_regexp *regex, const char *pattern)
 {
 	int error;
 
@@ -51,13 +52,11 @@ static int build_regex(p_regex_t *regex, const char *pattern)
 		return GIT_EINVALIDSPEC;
 	}
 
-	error = p_regcomp(regex, pattern, P_REG_EXTENDED);
+	error = git_regexp_compile(regex, pattern, 0);
 	if (!error)
 		return 0;
 
-	error = git_error_set_regex(regex, error);
-
-	p_regfree(regex);
+	git_regexp_dispose(regex);
 
 	return error;
 }
@@ -66,7 +65,7 @@ static int maybe_describe(git_object**out, git_repository *repo, const char *spe
 {
 	const char *substr;
 	int error;
-	p_regex_t regex;
+	git_regexp regex;
 
 	substr = strstr(spec, "-g");
 
@@ -76,8 +75,8 @@ static int maybe_describe(git_object**out, git_repository *repo, const char *spe
 	if (build_regex(&regex, ".+-[0-9]+-g[0-9a-fA-F]+") < 0)
 		return -1;
 
-	error = p_regexec(&regex, spec, 0, NULL, 0);
-	p_regfree(&regex);
+	error = git_regexp_match(&regex, spec);
+	git_regexp_dispose(&regex);
 
 	if (error)
 		return GIT_ENOTFOUND;
@@ -143,12 +142,11 @@ static int retrieve_previously_checked_out_branch_or_revision(git_object **out, 
 {
 	git_reference *ref = NULL;
 	git_reflog *reflog = NULL;
-	p_regex_t preg;
+	git_regexp preg;
 	int error = -1;
 	size_t i, numentries, cur;
 	const git_reflog_entry *entry;
 	const char *msg;
-	p_regmatch_t regexmatches[2];
 	git_buf buf = GIT_BUF_INIT;
 
 	cur = position;
@@ -168,12 +166,14 @@ static int retrieve_previously_checked_out_branch_or_revision(git_object **out, 
 	numentries  = git_reflog_entrycount(reflog);
 
 	for (i = 0; i < numentries; i++) {
+		git_regmatch regexmatches[2];
+
 		entry = git_reflog_entry_byindex(reflog, i);
 		msg = git_reflog_entry_message(entry);
 		if (!msg)
 			continue;
 
-		if (p_regexec(&preg, msg, 2, regexmatches, 0))
+		if (git_regexp_search(&preg, msg, 2, regexmatches) < 0)
 			continue;
 
 		cur--;
@@ -181,7 +181,8 @@ static int retrieve_previously_checked_out_branch_or_revision(git_object **out, 
 		if (cur > 0)
 			continue;
 
-		git_buf_put(&buf, msg+regexmatches[1].rm_so, regexmatches[1].rm_eo - regexmatches[1].rm_so);
+		if ((git_buf_put(&buf, msg+regexmatches[1].start, regexmatches[1].end - regexmatches[1].start)) < 0)
+			goto cleanup;
 
 		if ((error = git_reference_dwim(base_ref, repo, git_buf_cstr(&buf))) == 0)
 			goto cleanup;
@@ -199,7 +200,7 @@ static int retrieve_previously_checked_out_branch_or_revision(git_object **out, 
 cleanup:
 	git_reference_free(ref);
 	git_buf_dispose(&buf);
-	p_regfree(&preg);
+	git_regexp_dispose(&preg);
 	git_reflog_free(reflog);
 	return error;
 }
@@ -448,7 +449,7 @@ cleanup:
 	return error;
 }
 
-static int walk_and_search(git_object **out, git_revwalk *walk, p_regex_t *regex)
+static int walk_and_search(git_object **out, git_revwalk *walk, git_regexp *regex)
 {
 	int error;
 	git_oid oid;
@@ -460,7 +461,7 @@ static int walk_and_search(git_object **out, git_revwalk *walk, p_regex_t *regex
 		if ((error < 0) && (error != GIT_ENOTFOUND))
 			return -1;
 
-		if (!p_regexec(regex, git_commit_message((git_commit*)obj), 0, NULL, 0)) {
+		if (!git_regexp_match(regex, git_commit_message((git_commit*)obj))) {
 			*out = obj;
 			return 0;
 		}
@@ -476,7 +477,7 @@ static int walk_and_search(git_object **out, git_revwalk *walk, p_regex_t *regex
 
 static int handle_grep_syntax(git_object **out, git_repository *repo, const git_oid *spec_oid, const char *pattern)
 {
-	p_regex_t preg;
+	git_regexp preg;
 	git_revwalk *walk = NULL;
 	int error;
 
@@ -497,7 +498,7 @@ static int handle_grep_syntax(git_object **out, git_repository *repo, const git_
 	error = walk_and_search(out, walk, &preg);
 
 cleanup:
-	p_regfree(&preg);
+	git_regexp_dispose(&preg);
 	git_revwalk_free(walk);
 
 	return error;
diff --git a/src/userdiff.h b/src/userdiff.h
index 8bde630..c9a80d7 100644
--- a/src/userdiff.h
+++ b/src/userdiff.h
@@ -7,6 +7,8 @@
 #ifndef INCLUDE_userdiff_h__
 #define INCLUDE_userdiff_h__
 
+#include "regexp.h"
+
 /*
  * This file isolates the built in diff driver function name patterns.
  * Most of these patterns are taken from Git (with permission from the
@@ -29,7 +31,7 @@ typedef struct {
 #define PATTERNS(NAME, FN_PATS, WORD_PAT) \
 	{ NAME, FN_PATS, WORD_PAT WORD_DEFAULT, 0 }
 #define IPATTERN(NAME, FN_PATS, WORD_PAT) \
-	{ NAME, FN_PATS, WORD_PAT WORD_DEFAULT, P_REG_ICASE }
+	{ NAME, FN_PATS, WORD_PAT WORD_DEFAULT, GIT_REGEXP_ICASE }
 
 /*
  * The table of diff driver patterns
diff --git a/tests/core/posix.c b/tests/core/posix.c
index dcc619f..77ac65a 100644
--- a/tests/core/posix.c
+++ b/tests/core/posix.c
@@ -9,23 +9,12 @@
 # endif
 #endif
 
-#include <locale.h>
-
 #include "clar_libgit2.h"
 #include "futils.h"
 #include "posix.h"
-#include "userdiff.h"
-
-#if LC_ALL > 0
-static const char *old_locales[LC_ALL];
-#endif
 
 void test_core_posix__initialize(void)
 {
-#if LC_ALL > 0
-	memset(&old_locales, 0, sizeof(old_locales));
-#endif
-
 #ifdef GIT_WIN32
 	/* on win32, the WSA context needs to be initialized
 	 * before any socket calls can be performed */
@@ -156,115 +145,6 @@ void test_core_posix__utimes(void)
 	cl_must_pass(p_unlink("foo"));
 }
 
-static void try_set_locale(int category)
-{
-#if LC_ALL > 0
-	old_locales[category] = setlocale(category, NULL);
-#endif
-
-	if (!setlocale(category, "UTF-8") &&
-	    !setlocale(category, "c.utf8") &&
-	    !setlocale(category, "en_US.UTF-8"))
-		cl_skip();
-
-	if (MB_CUR_MAX == 1)
-		cl_fail("Expected locale to be switched to multibyte");
-}
-
-void test_core_posix__p_regcomp_ignores_global_locale_ctype(void)
-{
-	p_regex_t preg;
-
-	try_set_locale(LC_CTYPE);
-
-	cl_assert(!p_regcomp(&preg, "[\xc0-\xff][\x80-\xbf]", P_REG_EXTENDED));
-
-	p_regfree(&preg);
-}
-
-void test_core_posix__p_regcomp_ignores_global_locale_collate(void)
-{
-	p_regex_t preg;
-
-#ifdef GIT_WIN32
-	cl_skip();
-#endif
-
-	try_set_locale(LC_COLLATE);
-	cl_assert(!p_regcomp(&preg, "[\xc0-\xff][\x80-\xbf]", P_REG_EXTENDED));
-
-	p_regfree(&preg);
-}
-
-void test_core_posix__p_regcomp_matches_digits_with_locale(void)
-{
-	p_regex_t preg;
-	char c, str[2];
-
-#ifdef GIT_WIN32
-	cl_skip();
-#endif
-
-	try_set_locale(LC_COLLATE);
-	try_set_locale(LC_CTYPE);
-
-	cl_assert(!p_regcomp(&preg, "[[:digit:]]", P_REG_EXTENDED));
-
-	str[1] = '\0';
-	for (c = '0'; c <= '9'; c++) {
-	    str[0] = c;
-	    cl_assert(!p_regexec(&preg, str, 0, NULL, 0));
-	}
-
-	p_regfree(&preg);
-}
-
-void test_core_posix__p_regcomp_matches_alphabet_with_locale(void)
-{
-	p_regex_t preg;
-	char c, str[2];
-
-#ifdef GIT_WIN32
-	cl_skip();
-#endif
-
-	try_set_locale(LC_COLLATE);
-	try_set_locale(LC_CTYPE);
-
-	cl_assert(!p_regcomp(&preg, "[[:alpha:]]", P_REG_EXTENDED));
-
-	str[1] = '\0';
-	for (c = 'a'; c <= 'z'; c++) {
-	    str[0] = c;
-	    cl_assert(!p_regexec(&preg, str, 0, NULL, 0));
-	}
-	for (c = 'A'; c <= 'Z'; c++) {
-	    str[0] = c;
-	    cl_assert(!p_regexec(&preg, str, 0, NULL, 0));
-	}
-
-	p_regfree(&preg);
-}
-
-void test_core_posix__p_regcomp_compile_userdiff_regexps(void)
-{
-	size_t idx;
-
-	for (idx = 0; idx < ARRAY_SIZE(builtin_defs); ++idx) {
-		git_diff_driver_definition ddef = builtin_defs[idx];
-		int error = 0;
-		p_regex_t preg;
-
-		error = p_regcomp(&preg, ddef.fns, P_REG_EXTENDED | ddef.flags);
-		p_regfree(&preg);
-		cl_assert(!error);
-
-		error = p_regcomp(&preg, ddef.words, P_REG_EXTENDED);
-		p_regfree(&preg);
-		cl_assert(!error);
-	}
-}
-
 void test_core_posix__unlink_removes_symlink(void)
 {
 	if (!git_path_supports_symlinks(clar_sandbox_path()))
diff --git a/tests/core/regexp.c b/tests/core/regexp.c
new file mode 100644
index 0000000..8db5641
--- /dev/null
+++ b/tests/core/regexp.c
@@ -0,0 +1,213 @@
+#include "clar_libgit2.h"
+
+#include <locale.h>
+
+#include "regexp.h"
+#include "userdiff.h"
+
+#if LC_ALL > 0
+static const char *old_locales[LC_ALL];
+#endif
+
+static git_regexp regex;
+
+void test_core_regexp__initialize(void)
+{
+#if LC_ALL > 0
+	memset(&old_locales, 0, sizeof(old_locales));
+#endif
+}
+
+void test_core_regexp__cleanup(void)
+{
+	git_regexp_dispose(&regex);
+}
+
+static void try_set_locale(int category)
+{
+#if LC_ALL > 0
+	old_locales[category] = setlocale(category, NULL);
+#endif
+
+	if (!setlocale(category, "UTF-8") &&
+	    !setlocale(category, "c.utf8") &&
+	    !setlocale(category, "en_US.UTF-8"))
+		cl_skip();
+
+	if (MB_CUR_MAX == 1)
+		cl_fail("Expected locale to be switched to multibyte");
+}
+
+
+void test_core_regexp__compile_ignores_global_locale_ctype(void)
+{
+	try_set_locale(LC_CTYPE);
+	cl_git_pass(git_regexp_compile(&regex, "[\xc0-\xff][\x80-\xbf]", 0));
+}
+
+void test_core_regexp__compile_ignores_global_locale_collate(void)
+{
+#ifdef GIT_WIN32
+	cl_skip();
+#endif
+
+	try_set_locale(LC_COLLATE);
+	cl_git_pass(git_regexp_compile(&regex, "[\xc0-\xff][\x80-\xbf]", 0));
+}
+
+void test_core_regexp__regex_matches_digits_with_locale(void)
+{
+	char c, str[2];
+
+#ifdef GIT_WIN32
+	cl_skip();
+#endif
+
+	try_set_locale(LC_COLLATE);
+	try_set_locale(LC_CTYPE);
+
+	cl_git_pass(git_regexp_compile(&regex, "[[:digit:]]", 0));
+
+	str[1] = '\0';
+	for (c = '0'; c <= '9'; c++) {
+	    str[0] = c;
+	    cl_git_pass(git_regexp_match(&regex, str));
+	}
+}
+
+void test_core_regexp__regex_matches_alphabet_with_locale(void)
+{
+	char c, str[2];
+
+#ifdef GIT_WIN32
+	cl_skip();
+#endif
+
+	try_set_locale(LC_COLLATE);
+	try_set_locale(LC_CTYPE);
+
+	cl_git_pass(git_regexp_compile(&regex, "[[:alpha:]]", 0));
+
+	str[1] = '\0';
+	for (c = 'a'; c <= 'z'; c++) {
+	    str[0] = c;
+	    cl_git_pass(git_regexp_match(&regex, str));
+	}
+	for (c = 'A'; c <= 'Z'; c++) {
+	    str[0] = c;
+	    cl_git_pass(git_regexp_match(&regex, str));
+	}
+}
+
+void test_core_regexp__compile_userdiff_regexps(void)
+{
+	size_t idx;
+
+	for (idx = 0; idx < ARRAY_SIZE(builtin_defs); ++idx) {
+		git_diff_driver_definition ddef = builtin_defs[idx];
+
+		cl_git_pass(git_regexp_compile(&regex, ddef.fns, ddef.flags));
+		git_regexp_dispose(&regex);
+
+		cl_git_pass(git_regexp_compile(&regex, ddef.words, 0));
+		git_regexp_dispose(&regex);
+	}
+}
+
+void test_core_regexp__simple_search_matches(void)
+{
+	cl_git_pass(git_regexp_compile(&regex, "a", 0));
+	cl_git_pass(git_regexp_search(&regex, "a", 0, NULL));
+}
+
+void test_core_regexp__case_insensitive_search_matches(void)
+{
+	cl_git_pass(git_regexp_compile(&regex, "a", GIT_REGEXP_ICASE));
+	cl_git_pass(git_regexp_search(&regex, "A", 0, NULL));
+}
+
+void test_core_regexp__nonmatching_search_returns_error(void)
+{
+	cl_git_pass(git_regexp_compile(&regex, "a", 0));
+	cl_git_fail(git_regexp_search(&regex, "b", 0, NULL));
+}
+
+void test_core_regexp__search_finds_complete_match(void)
+{
+	git_regmatch matches[1];
+
+	cl_git_pass(git_regexp_compile(&regex, "abc", 0));
+	cl_git_pass(git_regexp_search(&regex, "abc", 1, matches));
+	cl_assert_equal_i(matches[0].start, 0);
+	cl_assert_equal_i(matches[0].end, 3);
+}
+
+void test_core_regexp__search_finds_correct_offsets(void)
+{
+	git_regmatch matches[3];
+
+	cl_git_pass(git_regexp_compile(&regex, "(a*)(b*)", 0));
+	cl_git_pass(git_regexp_search(&regex, "ab", 3, matches));
+	cl_assert_equal_i(matches[0].start, 0);
+	cl_assert_equal_i(matches[0].end, 2);
+	cl_assert_equal_i(matches[1].start, 0);
+	cl_assert_equal_i(matches[1].end, 1);
+	cl_assert_equal_i(matches[2].start, 1);
+	cl_assert_equal_i(matches[2].end, 2);
+}
+
+void test_core_regexp__search_finds_empty_group(void)
+{
+	git_regmatch matches[3];
+
+	cl_git_pass(git_regexp_compile(&regex, "(a*)(b*)c", 0));
+	cl_git_pass(git_regexp_search(&regex, "ac", 3, matches));
+	cl_assert_equal_i(matches[0].start, 0);
+	cl_assert_equal_i(matches[0].end, 2);
+	cl_assert_equal_i(matches[1].start, 0);
+	cl_assert_equal_i(matches[1].end, 1);
+	cl_assert_equal_i(matches[2].start, 1);
+	cl_assert_equal_i(matches[2].end, 1);
+}
+
+void test_core_regexp__search_fills_matches_with_first_matching_groups(void)
+{
+	git_regmatch matches[2];
+
+	cl_git_pass(git_regexp_compile(&regex, "(a)(b)(c)", 0));
+	cl_git_pass(git_regexp_search(&regex, "abc", 2, matches));
+	cl_assert_equal_i(matches[0].start, 0);
+	cl_assert_equal_i(matches[0].end, 3);
+	cl_assert_equal_i(matches[1].start, 0);
+	cl_assert_equal_i(matches[1].end, 1);
+}
+
+void test_core_regexp__search_skips_nonmatching_group(void)
+{
+	git_regmatch matches[4];
+
+	cl_git_pass(git_regexp_compile(&regex, "(a)(b)?(c)", 0));
+	cl_git_pass(git_regexp_search(&regex, "ac", 4, matches));
+	cl_assert_equal_i(matches[0].start, 0);
+	cl_assert_equal_i(matches[0].end, 2);
+	cl_assert_equal_i(matches[1].start, 0);
+	cl_assert_equal_i(matches[1].end, 1);
+	cl_assert_equal_i(matches[2].start, -1);
+	cl_assert_equal_i(matches[2].end, -1);
+	cl_assert_equal_i(matches[3].start, 1);
+	cl_assert_equal_i(matches[3].end, 2);
+}
+
+void test_core_regexp__search_initializes_trailing_nonmatching_groups(void)
+{
+	git_regmatch matches[3];
+
+	cl_git_pass(git_regexp_compile(&regex, "(a)bc", 0));
+	cl_git_pass(git_regexp_search(&regex, "abc", 3, matches));
+	cl_assert_equal_i(matches[0].start, 0);
+	cl_assert_equal_i(matches[0].end, 3);
+	cl_assert_equal_i(matches[1].start, 0);
+	cl_assert_equal_i(matches[1].end, 1);
+	cl_assert_equal_i(matches[2].start, -1);
+	cl_assert_equal_i(matches[2].end, -1);
+}