thodg/libgit2

diff --git a/include/git2/filter.h b/include/git2/filter.h
index 3bc4a90..478f3a6 100644
--- a/include/git2/filter.h
+++ b/include/git2/filter.h
@@ -39,7 +39,10 @@ typedef enum {
  * A filter that can transform file data
  *
  * This represents a filter that can be used to transform or even replace
- * file data.  Libgit2 currently includes one built in filter:
+ * file data.  Libgit2 includes one built in filter and it is possible to
+ * write your own (see git2/sys/filter.h for information on that).
+ *
+ * The built in filter is:
  *
  * * "crlf" which uses the complex rules with the "text", "eol", and
  *   "crlf" file attributes to decide how to convert between LF and CRLF
@@ -47,6 +50,17 @@ typedef enum {
  */
 typedef struct git_filter git_filter;
 
+GIT_EXTERN(git_filter *) git_filter_lookup(const char *name);
+
+#define GIT_FILTER_CRLF "crlf"
+
+GIT_EXTERN(int) git_filter_apply_to_buffer(
+	git_buffer *out,
+	git_filter *filter,
+	const git_buffer *input,
+	const char *as_path,
+	git_filter_mode_t mode);
+
 GIT_END_DECL
 
 /** @} */
diff --git a/include/git2/sys/filter.h b/include/git2/sys/filter.h
new file mode 100644
index 0000000..2264be0
--- /dev/null
+++ b/include/git2/sys/filter.h
@@ -0,0 +1,104 @@
+/*
+ * 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_sys_git_config_backend_h__
+#define INCLUDE_sys_git_config_backend_h__
+
+#include "git2/filter.h"
+
+/**
+ * @file git2/sys/filter.h
+ * @brief Git filter backend and plugin routines
+ * @defgroup git_backend Git custom backend APIs
+ * @ingroup Git
+ * @{
+ */
+GIT_BEGIN_DECL
+
+/**
+ * A filter source represents a file/blob to be processed
+ */
+typedef struct git_filter_source git_filter_source;
+struct git_filter_source {
+	git_repository *repo;
+	const char     *path;
+	git_oid         oid;  /* zero if unknown (which is likely) */
+	uint16_t        filemode; /* zero if unknown */
+};
+
+/**
+ * Callback to actually perform the data filtering
+ */
+typedef int (*git_filter_apply_fn)(
+	git_filter        *self,
+	void              **payload, /* may be read and/or set */
+	git_filter_mode_t mode,
+	git_buffer        *to,
+	const git_buffer  *from,
+	const git_filter_source *src);
+
+/**
+ * Callback to decide if a given source needs this filter
+ */
+typedef int (*git_filter_check_fn)(
+	git_filter        *self,
+	void              **payload, /* points to NULL ptr on entry, may be set */
+	git_filter_mode_t mode,
+	const git_filter_source *src);
+
+/**
+ * Callback to clean up after filtering has been applied
+ */
+typedef void (*git_filter_cleanup_fn)(
+	git_filter *self,
+	void       *payload);
+
+/**
+ * Filter structure used to register a new filter.
+ *
+ * To associate extra data with a filter, simply allocate extra data
+ * and put the `git_filter` struct at the start of your data buffer,
+ * then cast the `self` pointer to your larger structure when your
+ * callback is invoked.
+ *
+ * `version` should be set to GIT_FILTER_VERSION
+ *
+ * `apply` is the callback that actually filters data.
+ *
+ * `check` is an optional callback that checks if filtering is needed for
+ * a given source.
+ *
+ * `cleanup` is an optional callback that is made after the filter has
+ * been applied.  Both the `check` and `apply` callbacks are able to
+ * allocate a `payload` to keep per-source filter state, and this callback
+ * is given that value and can clean up as needed.
+ */
+struct git_filter {
+	unsigned int          version;
+	git_filter_apply_fn   apply;
+	git_filter_check_fn   check;
+	git_filter_cleanup_fn cleanup;
+};
+
+#define GIT_FILTER_VERSION 1
+
+/**
+ * Register a filter under a given name
+ *
+ * Two filters will be preregistered with libgit2: GIT_FILTER_CRLF and
+ * GIT_FILTER_IDENT.
+ */
+GIT_EXTERN(int) git_filter_register(
+	const char *name, const git_filter *filter);
+
+/**
+ * Remove the filter with the given name
+ */
+GIT_EXTERN(int) git_filter_unregister(const char *name);
+
+/** @} */
+GIT_END_DECL
+#endif
diff --git a/src/blob.c b/src/blob.c
index 6a86653..3581ee9 100644
--- a/src/blob.c
+++ b/src/blob.c
@@ -108,7 +108,7 @@ static int write_file_filtered(
 	git_off_t *size,
 	git_odb *odb,
 	const char *full_path,
-	git_vector *filters)
+	git_filter_list *fl)
 {
 	int error;
 	git_buf source = GIT_BUF_INIT;
@@ -117,7 +117,7 @@ static int write_file_filtered(
 	if ((error = git_futils_readbuffer(&source, full_path)) < 0)
 		return error;
 
-	error = git_filters_apply(&dest, &source, filters);
+	error = git_filter_list_apply(&dest, &source, fl);
 
 	/* Free the source as soon as possible. This can be big in memory,
 	 * and we don't want to ODB write to choke */
@@ -198,29 +198,25 @@ int git_blob__create_from_paths(
 	if (S_ISLNK(mode)) {
 		error = write_symlink(oid, odb, content_path, (size_t)size);
 	} else {
-		git_vector write_filters = GIT_VECTOR_INIT;
-		int filter_count = 0;
+		git_filter_list *fl = NULL;
 
-		if (try_load_filters) {
+		if (try_load_filters)
 			/* Load the filters for writing this file to the ODB */
-			filter_count = git_filters_load(
-				&write_filters, repo, hint_path, GIT_FILTER_TO_ODB);
-		}
+			error = git_filter_list_load(
+				&fl, repo, hint_path, GIT_FILTER_TO_ODB);
 
-		if (filter_count < 0) {
-			/* Negative value means there was a critical error */
-			error = filter_count;
-		} else if (filter_count == 0) {
+		if (error < 0)
+			/* well, that didn't work */;
+		else if (fl == NULL)
 			/* No filters need to be applied to the document: we can stream
 			 * directly from disk */
 			error = write_file_stream(oid, odb, content_path, size);
-		} else {
+		else {
 			/* We need to apply one or more filters */
-			error = write_file_filtered(
-				oid, &size, odb, content_path, &write_filters);
-		}
+			error = write_file_filtered(oid, &size, odb, content_path, fl);
 
-		git_filters_free(&write_filters);
+			git_filter_list_free(fl);
+		}
 
 		/*
 		 * TODO: eventually support streaming filtered files, for files
@@ -345,9 +341,9 @@ int git_blob_filtered_content(
 	const char *as_path,
 	int check_for_binary_data)
 {
-	int error = 0, num_filters = 0;
+	int error = 0;
 	git_buf filtered = GIT_BUF_INIT, unfiltered = GIT_BUF_INIT;
-	git_vector filters = GIT_VECTOR_INIT;
+	git_filter_list *fl = NULL;
 
 	assert(blob && as_path && out);
 
@@ -359,12 +355,12 @@ int git_blob_filtered_content(
 	if (check_for_binary_data && git_buf_text_is_binary(&filtered))
 		return 0;
 
-	num_filters = git_filters_load(
-		&filters, git_blob_owner(blob), as_path, GIT_FILTER_TO_WORKTREE);
-	if (num_filters < 0)
-		return num_filters;
+	error = git_filter_list_load(
+		&fl, git_blob_owner(blob), as_path, GIT_FILTER_TO_WORKTREE);
+	if (error < 0)
+		return error;
 
-	if (num_filters > 0) {
+	if (fl != NULL) {
 		if (out->ptr && out->available) {
 			filtered.ptr   = out->ptr;
 			filtered.size  = out->size;
@@ -374,9 +370,9 @@ int git_blob_filtered_content(
 		}
 
 		if (!(error = git_blob__getbuf(&unfiltered, blob)))
-			error = git_filters_apply(&filtered, &unfiltered, &filters);
+			error = git_filter_list_apply(&filtered, &unfiltered, fl);
 
-		git_filters_free(&filters);
+		git_filter_list_free(fl);
 		git_buf_free(&unfiltered);
 	}
 
diff --git a/src/buffer.h b/src/buffer.h
index f3e1d50..b1cb5d0 100644
--- a/src/buffer.h
+++ b/src/buffer.h
@@ -9,6 +9,7 @@
 
 #include "common.h"
 #include "git2/strarray.h"
+#include "git2/buffer.h"
 #include <stdarg.h>
 
 typedef struct {
@@ -174,4 +175,25 @@ int git_buf_splice(
 	const char *data,
 	size_t nb_to_insert);
 
+
+#define GIT_BUF_FROM_BUFFER(buffer) \
+	{ (buffer)->ptr, (buffer)->available, (buffer)->size }
+
+GIT_INLINE(void) git_buf_from_buffer(git_buf *buf, const git_buffer *buffer)
+{
+	buf->ptr   = buffer->ptr;
+	buf->size  = buffer->size;
+	buf->asize = buffer->available;
+}
+
+#define GIT_BUFFER_FROM_BUF(buf) \
+	{ (buf)->ptr, (buf)->size, (buf)->asize }
+
+GIT_INLINE(void) git_buffer_from_buf(git_buffer *buffer, const git_buf *buf)
+{
+	buffer->ptr  = buf->ptr;
+	buffer->size = buf->size;
+	buffer->available = buf->asize;
+}
+
 #endif
diff --git a/src/checkout.c b/src/checkout.c
index eb92e8f..5ce4a19 100644
--- a/src/checkout.c
+++ b/src/checkout.c
@@ -710,56 +710,40 @@ static int blob_content_to_file(
 	mode_t entry_filemode,
 	git_checkout_opts *opts)
 {
-	int error = -1, nb_filters = 0;
-	mode_t file_mode = opts->file_mode;
-	bool dont_free_filtered;
+	int error = 0;
+	mode_t file_mode = opts->file_mode ? opts->file_mode : entry_filemode;
 	git_buf unfiltered = GIT_BUF_INIT, filtered = GIT_BUF_INIT;
-	git_vector filters = GIT_VECTOR_INIT;
+	git_filter_list *fl = NULL;
 
 	/* Create a fake git_buf from the blob raw data... */
 	filtered.ptr  = (void *)git_blob_rawcontent(blob);
 	filtered.size = (size_t)git_blob_rawsize(blob);
-	/* ... and make sure it doesn't get unexpectedly freed */
-	dont_free_filtered = true;
-
-	if (!opts->disable_filters &&
-		!git_buf_text_is_binary(&filtered) &&
-		(nb_filters = git_filters_load(
-			&filters,
-			git_object_owner((git_object *)blob),
-			path,
-			GIT_FILTER_TO_WORKTREE)) > 0)
-	{
+
+	if (!opts->disable_filters && !git_buf_text_is_binary(&filtered)) {
+		error = git_filter_list_load(
+			&fl, git_blob_owner(blob), path, GIT_FILTER_TO_WORKTREE);
+	}
+
+	if (fl != NULL) {
 		/* reset 'filtered' so it can be a filter target */
 		git_buf_init(&filtered, 0);
-		dont_free_filtered = false;
-	}
 
-	if (nb_filters < 0)
-		return nb_filters;
+		if (!(error = git_blob__getbuf(&unfiltered, blob))) {
+			error = git_filter_list_apply(&filtered, &unfiltered, fl);
 
-	if (nb_filters > 0)	 {
-		if ((error = git_blob__getbuf(&unfiltered, blob)) < 0)
-			goto cleanup;
+			git_buf_free(&unfiltered);
+		}
 
-		if ((error = git_filters_apply(&filtered, &unfiltered, &filters)) < 0)
-			goto cleanup;
+		git_filter_list_free(fl);
 	}
 
-	/* Allow overriding of file mode */
-	if (!file_mode)
-		file_mode = entry_filemode;
-
-	error = buffer_to_file(
-		st, &filtered, path, opts->dir_mode, opts->file_open_flags, file_mode);
-
-	if (!error)
+	if (!error &&
+		!(error = buffer_to_file(
+			st, &filtered, path, opts->dir_mode,
+			opts->file_open_flags, file_mode)))
 		st->st_mode = entry_filemode;
 
-cleanup:
-	git_filters_free(&filters);
-	git_buf_free(&unfiltered);
-	if (!dont_free_filtered)
+	if (filtered.asize != 0)
 		git_buf_free(&filtered);
 
 	return error;
diff --git a/src/crlf.c b/src/crlf.c
index fbb3ba2..2177bff 100644
--- a/src/crlf.c
+++ b/src/crlf.c
@@ -19,13 +19,11 @@
 struct crlf_attrs {
 	int crlf_action;
 	int eol;
+	int auto_crlf;
 };
 
 struct crlf_filter {
 	git_filter f;
-	struct crlf_attrs attrs;
-	git_repository *repo;
-	char path[GIT_FLEX_ARRAY];
 };
 
 static int check_crlf(const char *value)
@@ -76,7 +74,8 @@ static int crlf_input_action(struct crlf_attrs *ca)
 	return ca->crlf_action;
 }
 
-static int crlf_load_attributes(struct crlf_attrs *ca, git_repository *repo, const char *path)
+static int crlf_load_attributes(
+	struct crlf_attrs *ca, git_repository *repo, const char *path)
 {
 #define NUM_CONV_ATTRS 3
 
@@ -108,9 +107,8 @@ static int crlf_load_attributes(struct crlf_attrs *ca, git_repository *repo, con
 	return -1;
 }
 
-static int has_cr_in_index(git_filter *self)
+static int has_cr_in_index(git_repository *repo, const char *path)
 {
-	struct crlf_filter *filter = (struct crlf_filter *)self;
 	git_index *index;
 	const git_index_entry *entry;
 	git_blob *blob;
@@ -118,19 +116,19 @@ static int has_cr_in_index(git_filter *self)
 	git_off_t blobsize;
 	bool found_cr;
 
-	if (git_repository_index__weakptr(&index, filter->repo) < 0) {
+	if (git_repository_index__weakptr(&index, repo) < 0) {
 		giterr_clear();
 		return false;
 	}
 
-	if (!(entry = git_index_get_bypath(index, filter->path, 0)) &&
-		!(entry = git_index_get_bypath(index, filter->path, 1)))
+	if (!(entry = git_index_get_bypath(index, path, 0)) &&
+		!(entry = git_index_get_bypath(index, path, 1)))
 		return false;
 
 	if (!S_ISREG(entry->mode)) /* don't crlf filter non-blobs */
 		return true;
 
-	if (git_blob_lookup(&blob, filter->repo, &entry->oid) < 0)
+	if (git_blob_lookup(&blob, repo, &entry->oid) < 0)
 		return false;
 
 	blobcontent = git_blob_rawcontent(blob);
@@ -147,26 +145,26 @@ static int has_cr_in_index(git_filter *self)
 }
 
 static int crlf_apply_to_odb(
-	git_filter *self, git_buf *dest, const git_buf *source)
+	struct crlf_attrs *ca,
+	git_buffer *to,
+	const git_buffer *from,
+	const git_filter_source *src)
 {
-	struct crlf_filter *filter = (struct crlf_filter *)self;
-
-	assert(self && dest && source);
+	const git_buf from_buf = GIT_BUF_FROM_BUFFER(from);
+	git_buf to_buf = GIT_BUF_FROM_BUFFER(to);
 
 	/* Empty file? Nothing to do */
-	if (git_buf_len(source) == 0)
+	if (!git_buf_len(&from_buf))
 		return 0;
 
 	/* Heuristics to see if we can skip the conversion.
 	 * Straight from Core Git.
 	 */
-	if (filter->attrs.crlf_action == GIT_CRLF_AUTO ||
-		filter->attrs.crlf_action == GIT_CRLF_GUESS) {
-
+	if (ca->crlf_action == GIT_CRLF_AUTO || ca->crlf_action == GIT_CRLF_GUESS) {
 		git_buf_text_stats stats;
 
 		/* Check heuristics for binary vs text... */
-		if (git_buf_text_gather_stats(&stats, source, false))
+		if (git_buf_text_gather_stats(&stats, &from_buf, false))
 			return -1;
 
 		/*
@@ -175,28 +173,34 @@ static int crlf_apply_to_odb(
 		 * stuff?
 		 */
 		if (stats.cr != stats.crlf)
-			return -1;
+			return GIT_ENOTFOUND;
 
-		if (filter->attrs.crlf_action == GIT_CRLF_GUESS) {
+		if (ca->crlf_action == GIT_CRLF_GUESS) {
 			/*
 			 * If the file in the index has any CR in it, do not convert.
 			 * This is the new safer autocrlf handling.
 			 */
-			if (has_cr_in_index(self))
-				return -1;
+			if (has_cr_in_index(src->repo, src->path))
+				return GIT_ENOTFOUND;
 		}
 
 		if (!stats.cr)
-			return -1;
+			return GIT_ENOTFOUND;
 	}
 
 	/* Actually drop the carriage returns */
-	return git_buf_text_crlf_to_lf(dest, source);
+	if (git_buf_text_crlf_to_lf(&to_buf, &from_buf) < 0)
+		return -1;
+
+	/* Overwrite "to" buffer in case data was resized */
+	git_buffer_from_buf(to, &to_buf);
+
+	return 0;
 }
 
-static const char *line_ending(struct crlf_filter *filter)
+static const char *line_ending(struct crlf_attrs *ca)
 {
-	switch (filter->attrs.crlf_action) {
+	switch (ca->crlf_action) {
 	case GIT_CRLF_BINARY:
 	case GIT_CRLF_INPUT:
 		return "\n";
@@ -213,7 +217,7 @@ static const char *line_ending(struct crlf_filter *filter)
 		goto line_ending_error;
 	}
 
-	switch (filter->attrs.eol) {
+	switch (ca->eol) {
 	case GIT_EOL_UNSET:
 		return GIT_EOL_NATIVE == GIT_EOL_CRLF
 			? "\r\n"
@@ -235,44 +239,58 @@ line_ending_error:
 }
 
 static int crlf_apply_to_workdir(
-	git_filter *self, git_buf *tgt, const git_buf *src)
+	struct crlf_attrs *ca, git_buffer *to, const git_buffer *from)
 {
-	struct crlf_filter *filter = (struct crlf_filter *)self;
+	const git_buf from_buf = GIT_BUF_FROM_BUFFER(from);
+	git_buf to_buf = GIT_BUF_FROM_BUFFER(to);
 	const char *workdir_ending = NULL;
 
-	assert(self && tgt && src);
-
 	/* Empty file? Nothing to do. */
-	if (git_buf_len(src) == 0)
-		return -1;
+	if (git_buf_len(&from_buf) == 0)
+		return 0;
 
 	/* Determine proper line ending */
-	workdir_ending = line_ending(filter);
+	workdir_ending = line_ending(ca);
 	if (!workdir_ending)
 		return -1;
 
 	if (!strcmp("\n", workdir_ending)) {
-		if (git_buf_find(src, '\r') < 0)
+		if (ca->crlf_action == GIT_CRLF_GUESS && ca->auto_crlf)
+			return GIT_ENOTFOUND;
+
+		if (git_buf_find(&from_buf, '\r') < 0)
+			return GIT_ENOTFOUND;
+
+		if (git_buf_text_crlf_to_lf(&to_buf, &from_buf) < 0)
+			return -1;
+	} else {
+		/* only other supported option is lf->crlf conversion */
+		assert(!strcmp("\r\n", workdir_ending));
+
+		if (git_buf_text_lf_to_crlf(&to_buf, &from_buf) < 0)
 			return -1;
-		return git_buf_text_crlf_to_lf(tgt, src);
 	}
 
-	/* only other supported option is lf->crlf conversion */
-	assert(!strcmp("\r\n", workdir_ending));
-	return git_buf_text_lf_to_crlf(tgt, src);
+	/* Overwrite "to" buffer in case data was resized */
+	git_buffer_from_buf(to, &to_buf);
+
+	return 0;
 }
 
-static int find_and_add_filter(
-	git_vector *filters, git_repository *repo, const char *path,
-	int (*apply)(struct git_filter *self, git_buf *tgt, const git_buf *src))
+static int crlf_check(
+	git_filter        *self,
+	void              **payload, /* points to NULL ptr on entry, may be set */
+	git_filter_mode_t mode,
+	const git_filter_source *src)
 {
-	struct crlf_attrs ca;
-	struct crlf_filter *filter;
-	size_t pathlen;
 	int error;
+	struct crlf_attrs ca;
+
+	GIT_UNUSED(self);
+	GIT_UNUSED(mode);
 
 	/* Load gitattributes for the path */
-	if ((error = crlf_load_attributes(&ca, repo, path)) < 0)
+	if ((error = crlf_load_attributes(&ca, src->repo, src->path)) < 0)
 		return error;
 
 	/*
@@ -282,41 +300,54 @@ static int find_and_add_filter(
 	ca.crlf_action = crlf_input_action(&ca);
 
 	if (ca.crlf_action == GIT_CRLF_BINARY)
-		return 0;
+		return GIT_ENOTFOUND;
 
 	if (ca.crlf_action == GIT_CRLF_GUESS) {
-		int auto_crlf;
-
-		if ((error = git_repository__cvar(&auto_crlf, repo, GIT_CVAR_AUTO_CRLF)) < 0)
+		if ((error = git_repository__cvar(
+				&ca.auto_crlf, src->repo, GIT_CVAR_AUTO_CRLF)) < 0)
 			return error;
 
-		if (auto_crlf == GIT_AUTO_CRLF_FALSE)
-			return 0;
+		if (ca.auto_crlf == GIT_AUTO_CRLF_FALSE)
+			return GIT_ENOTFOUND;
 	}
 
-	/* If we're good, we create a new filter object and push it
-	 * into the filters array */
-	pathlen = strlen(path);
-	filter = git__malloc(sizeof(struct crlf_filter) + pathlen + 1);
-	GITERR_CHECK_ALLOC(filter);
+	*payload = git__malloc(sizeof(ca));
+	GITERR_CHECK_ALLOC(*payload);
+	memcpy(*payload, &ca, sizeof(ca));
 
-	filter->f.apply = apply;
-	filter->f.do_free = NULL;
-	memcpy(&filter->attrs, &ca, sizeof(struct crlf_attrs));
-	filter->repo = repo;
-	memcpy(filter->path, path, pathlen + 1);
+	return 0;
+}
+
+static int crlf_apply(
+	git_filter        *self,
+	void              **payload, /* may be read and/or set */
+	git_filter_mode_t mode,
+	git_buffer        *to,
+	const git_buffer  *from,
+	const git_filter_source *src)
+{
+	GIT_UNUSED(self);
 
-	return git_vector_insert(filters, filter);
+	if (mode == GIT_FILTER_SMUDGE)
+		return crlf_apply_to_workdir(*payload, to, from);
+	else
+		return crlf_apply_to_odb(*payload, to, from, src);
 }
 
-int git_filter_add__crlf_to_odb(
-	git_vector *filters, git_repository *repo, const char *path)
+static void crlf_cleanup(
+	git_filter *self,
+	void       *payload)
 {
-	return find_and_add_filter(filters, repo, path, &crlf_apply_to_odb);
+	GIT_UNUSED(self);
+	git__free(payload);
 }
 
-int git_filter_add__crlf_to_workdir(
-	git_vector *filters, git_repository *repo, const char *path)
+git_filter *git_crlf_filter_new(void)
 {
-	return find_and_add_filter(filters, repo, path, &crlf_apply_to_workdir);
+	struct crlf_filter *f = git__calloc(1, sizeof(struct crlf_filter));
+	f->f.version = GIT_FILTER_VERSION;
+	f->f.check   = crlf_check;
+	f->f.apply   = crlf_apply;
+	f->f.cleanup = crlf_cleanup;
+	return (git_filter *)f;
 }
diff --git a/src/diff.c b/src/diff.c
index 77dbbd8..b1cde36 100644
--- a/src/diff.c
+++ b/src/diff.c
@@ -568,21 +568,21 @@ int git_diff__oid_for_file(
 		giterr_set(GITERR_OS, "File size overflow (for 32-bits) on '%s'", path);
 		result = -1;
 	} else {
-		git_vector filters = GIT_VECTOR_INIT;
+		git_filter_list *fl = NULL;
 
-		result = git_filters_load(&filters, repo, path, GIT_FILTER_TO_ODB);
-		if (result >= 0) {
+		result = git_filter_list_load(&fl, repo, path, GIT_FILTER_TO_ODB);
+		if (!result) {
 			int fd = git_futils_open_ro(full_path.ptr);
 			if (fd < 0)
 				result = fd;
 			else {
 				result = git_odb__hashfd_filtered(
-					oid, fd, (size_t)size, GIT_OBJ_BLOB, &filters);
+					oid, fd, (size_t)size, GIT_OBJ_BLOB, fl);
 				p_close(fd);
 			}
-		}
 
-		git_filters_free(&filters);
+			git_filter_list_free(fl);
+		}
 	}
 
 cleanup:
diff --git a/src/diff_file.c b/src/diff_file.c
index bcfef13..7602591 100644
--- a/src/diff_file.c
+++ b/src/diff_file.c
@@ -296,7 +296,7 @@ static int diff_file_content_load_workdir_file(
 	git_diff_file_content *fc, git_buf *path)
 {
 	int error = 0;
-	git_vector filters = GIT_VECTOR_INIT;
+	git_filter_list *fl = NULL;
 	git_buf raw = GIT_BUF_INIT, filtered = GIT_BUF_INIT;
 	git_file fd = git_futils_open_ro(git_buf_cstr(path));
 
@@ -310,41 +310,35 @@ static int diff_file_content_load_workdir_file(
 	if (diff_file_content_binary_by_size(fc))
 		goto cleanup;
 
-	if ((error = git_filters_load(
-			&filters, fc->repo, fc->file->path, GIT_FILTER_TO_ODB)) < 0)
+	if ((error = git_filter_list_load(
+			&fl, fc->repo, fc->file->path, GIT_FILTER_TO_ODB)) < 0)
 		goto cleanup;
-	/* error >= is a filter count */
 
-	if (error == 0) {
+	/* if there are no filters, try to mmap the file */
+	if (fl == NULL) {
 		if (!(error = git_futils_mmap_ro(
-				&fc->map, fd, 0, (size_t)fc->file->size)))
+				&fc->map, fd, 0, (size_t)fc->file->size))) {
 			fc->flags |= GIT_DIFF_FLAG__UNMAP_DATA;
-		else /* fall through to try readbuffer below */
-			giterr_clear();
-	}
-
-	if (error != 0) {
-		error = git_futils_readbuffer_fd(&raw, fd, (size_t)fc->file->size);
-		if (error < 0)
 			goto cleanup;
-
-		if (!filters.length)
-			git_buf_swap(&filtered, &raw);
-		else
-			error = git_filters_apply(&filtered, &raw, &filters);
-
-		if (!error) {
-			fc->map.len  = git_buf_len(&filtered);
-			fc->map.data = git_buf_detach(&filtered);
-			fc->flags |= GIT_DIFF_FLAG__FREE_DATA;
 		}
 
-		git_buf_free(&raw);
-		git_buf_free(&filtered);
+		/* if mmap failed, fall through to try readbuffer below */
+		giterr_clear();
 	}
 
+	if (!(error = git_futils_readbuffer_fd(&raw, fd, (size_t)fc->file->size)) &&
+		!(error = git_filter_list_apply(&filtered, &raw, fl)))
+	{
+		fc->map.len  = git_buf_len(&filtered);
+		fc->map.data = git_buf_detach(&filtered);
+		fc->flags |= GIT_DIFF_FLAG__FREE_DATA;
+	}
+
+	git_buf_free(&raw);
+	git_buf_free(&filtered);
+
 cleanup:
-	git_filters_free(&filters);
+	git_filter_list_free(fl);
 	p_close(fd);
 
 	return error;
diff --git a/src/filter.c b/src/filter.c
index 9f749dc..7935e65 100644
--- a/src/filter.c
+++ b/src/filter.c
@@ -13,62 +13,155 @@
 #include "git2/config.h"
 #include "blob.h"
 
-int git_filters_load(git_vector *filters, git_repository *repo, const char *path, int mode)
+typedef struct {
+	git_filter *filter;
+	void *payload;
+} git_filter_entry;
+
+struct git_filter_list {
+	git_array_t(git_filter_entry) filters;
+	git_filter_mode_t mode;
+	git_filter_source source;
+	char path[GIT_FLEX_ARRAY];
+};
+
+typedef struct {
+	const char *filter_name;
+	git_filter *filter;
+} git_filter_def;
+
+static git_array_t(git_filter_def) filter_registry = GIT_ARRAY_INIT;
+
+static int filter_load_defaults(void)
 {
-	int error;
-
-	if (mode == GIT_FILTER_TO_ODB) {
-		/* Load the CRLF cleanup filter when writing to the ODB */
-		error = git_filter_add__crlf_to_odb(filters, repo, path);
-		if (error < 0)
-			return error;
-	} else {
-		error = git_filter_add__crlf_to_workdir(filters, repo, path);
-		if (error < 0)
-			return error;
+	if (!git_array_size(filter_registry)) {
+		git_filter_def *fdef = git_array_alloc(filter_registry);
+		GITERR_CHECK_ALLOC(fdef);
+
+		fdef->filter_name = GIT_FILTER_CRLF;
+		fdef->filter = git_crlf_filter_new();
+		GITERR_CHECK_ALLOC(fdef->filter);
 	}
 
-	return (int)filters->length;
+	return 0;
 }
 
-void git_filters_free(git_vector *filters)
+static int git_filter_list_new(
+	git_filter_list **out, git_filter_mode_t mode, const git_filter_source *src)
 {
-	size_t i;
-	git_filter *filter;
+	git_filter_list *fl = NULL;
+	size_t pathlen = src->path ? strlen(src->path) : 0;
+
+	fl = git__calloc(1, sizeof(git_filter_list) + pathlen + 1);
+	GITERR_CHECK_ALLOC(fl);
+
+	fl->mode = mode;
+	if (src->path)
+		memcpy(fl->path, src->path, pathlen);
+	fl->source.repo = src->repo;
+	fl->source.path = fl->path;
+
+	*out = fl;
+	return 0;
+}
+
+int git_filter_list_load(
+	git_filter_list **filters,
+	git_repository *repo,
+	const char *path,
+	git_filter_mode_t mode)
+{
+	int error = 0;
+	git_filter_list *fl = NULL;
+	git_filter_source src = { 0 };
+	git_filter_entry *fe;
+	uint32_t f;
+
+	if (filter_load_defaults() < 0)
+		return -1;
+
+	src.repo = repo;
+	src.path = path;
+
+	for (f = 0; f < git_array_size(filter_registry); ++f) {
+		void *payload = NULL;
+		git_filter_def *fdef = git_array_get(filter_registry, f);
+
+		if (!fdef || !fdef->filter)
+			continue;
 
-	git_vector_foreach(filters, i, filter) {
-		if (filter->do_free != NULL)
-			filter->do_free(filter);
-		else
-			git__free(filter);
+		if (fdef->filter->check)
+			error = fdef->filter->check(fdef->filter, &payload, mode, &src);
+
+		if (error == GIT_ENOTFOUND)
+			error = 0;
+		else if (error < 0)
+			break;
+		else {
+			if (!fl && (error = git_filter_list_new(&fl, mode, &src)) < 0)
+				return error;
+
+			fe = git_array_alloc(fl->filters);
+			GITERR_CHECK_ALLOC(fe);
+			fe->filter  = fdef->filter;
+			fe->payload = payload;
+		}
+	}
+
+	if (error && fl != NULL) {
+		git_array_clear(fl->filters);
+		git__free(fl);
+		fl = NULL;
+	}
+
+	*filters = fl;
+	return error;
+}
+
+void git_filter_list_free(git_filter_list *fl)
+{
+	uint32_t i;
+
+	if (!fl)
+		return;
+
+	for (i = 0; i < git_array_size(fl->filters); ++i) {
+		git_filter_entry *fe = git_array_get(fl->filters, i);
+		if (fe->filter->cleanup)
+			fe->filter->cleanup(fe->filter, fe->payload);
 	}
 
-	git_vector_free(filters);
+	git_array_clear(fl->filters);
+	git__free(fl);
 }
 
-int git_filters_apply(git_buf *dest, git_buf *source, git_vector *filters)
+int git_filter_list_apply(
+	git_buf *dest,
+	git_buf *source,
+	git_filter_list *fl)
 {
-	size_t i;
+	int error = 0;
+	uint32_t i;
 	unsigned int src;
 	git_buf *dbuffer[2];
 
+	if (!fl) {
+		git_buf_swap(dest, source);
+		return 0;
+	}
+
 	dbuffer[0] = source;
 	dbuffer[1] = dest;
 
 	src = 0;
 
-	if (git_buf_len(source) == 0) {
-		git_buf_clear(dest);
-		return 0;
-	}
-
 	/* Pre-grow the destination buffer to more or less the size
 	 * we expect it to have */
 	if (git_buf_grow(dest, git_buf_len(source)) < 0)
 		return -1;
 
-	for (i = 0; i < filters->length; ++i) {
-		git_filter *filter = git_vector_get(filters, i);
+	for (i = 0; i < git_array_size(fl->filters); ++i) {
+		git_filter_entry *fe = git_array_get(fl->filters, i);
 		unsigned int dst = 1 - src;
 
 		git_buf_clear(dbuffer[dst]);
@@ -79,8 +172,25 @@ int git_filters_apply(git_buf *dest, git_buf *source, git_vector *filters)
 		 * of the double buffering (so that the text goes through
 		 * cleanly).
 		 */
-		if (filter->apply(filter, dbuffer[dst], dbuffer[src]) == 0)
-			src = dst;
+		{
+			git_buffer srcb = GIT_BUFFER_FROM_BUF(dbuffer[src]);
+			git_buffer dstb = GIT_BUFFER_FROM_BUF(dbuffer[dst]);
+
+			error = fe->filter->apply(
+				fe->filter, &fe->payload, fl->mode, &dstb, &srcb, &fl->source);
+
+			if (error == GIT_ENOTFOUND)
+				error = 0;
+			else if (error < 0) {
+				git_buf_clear(dest);
+				return error;
+			}
+			else {
+				git_buf_from_buffer(dbuffer[src], &srcb);
+				git_buf_from_buffer(dbuffer[dst], &dstb);
+				src = dst;
+			}
+		}
 
 		if (git_buf_oom(dbuffer[dst]))
 			return -1;
diff --git a/src/filter.h b/src/filter.h
index 67845ad..a4ee217 100644
--- a/src/filter.h
+++ b/src/filter.h
@@ -9,14 +9,11 @@
 
 #include "common.h"
 #include "buffer.h"
+#include "array.h"
 #include "git2/odb.h"
 #include "git2/repository.h"
 #include "git2/filter.h"
-
-struct git_filter {
-	int (*apply)(struct git_filter *self, git_buf *dest, const git_buf *source);
-	void (*do_free)(struct git_filter *self);
-};
+#include "git2/sys/filter.h"
 
 typedef enum {
 	GIT_CRLF_GUESS = -1,
@@ -27,34 +24,38 @@ typedef enum {
 	GIT_CRLF_AUTO,
 } git_crlf_t;
 
+typedef struct git_filter_list git_filter_list;
+
 /*
  * FILTER API
  */
 
 /*
- * For any given path in the working directory, fill the `filters`
- * array with the relevant filters that need to be applied.
+ * For any given path in the working directory, create a `git_filter_list`
+ * with the relevant filters that need to be applied.
  *
- * Mode is either `GIT_FILTER_TO_WORKTREE` if you need to load the
- * filters that will be used when checking out a file to the working
- * directory, or `GIT_FILTER_TO_ODB` for the filters used when writing
- * a file to the ODB.
+ * This will return 0 (success) but set the output git_filter_list to NULL
+ * if no filters are requested for the given file.
  *
- * @param filters Vector where to store all the loaded filters
+ * @param filters Output newly created git_filter_list (or NULL)
  * @param repo Repository object that contains `path`
  * @param path Relative path of the file to be filtered
  * @param mode Filtering direction (WT->ODB or ODB->WT)
- * @return the number of filters loaded for the file (0 if the file
- *	doesn't need filtering), or a negative error code
+ * @return 0 on success (which could still return NULL if no filters are
+ *         needed for the requested file), <0 on error
  */
-extern int git_filters_load(git_vector *filters, git_repository *repo, const char *path, int mode);
+extern int git_filter_list_load(
+	git_filter_list **filters,
+	git_repository *repo,
+	const char *path,
+	git_filter_mode_t mode);
 
 /*
- * Apply one or more filters to a file.
+ * Apply one or more filters to a data buffer.
  *
- * The file must have been loaded as a `git_buf` object. Both the `source`
- * and `dest` buffers are owned by the caller and must be freed once
- * they are no longer needed.
+ * The source data must have been loaded as a `git_buf` object. Both the
+ * `source` and `dest` buffers are owned by the caller and must be freed
+ * once they are no longer needed.
  *
  * NOTE: Because of the double-buffering schema, the `source` buffer that
  * contains the original file may be tampered once the filtering is
@@ -63,29 +64,25 @@ extern int git_filters_load(git_vector *filters, git_repository *repo, const cha
  *
  * @param dest Buffer to store the result of the filtering
  * @param source Buffer containing the document to filter
- * @param filters Vector of filters as supplied by `git_filters_load`
+ * @param filters An already loaded git_filter_list
  * @return 0 on success, an error code otherwise
  */
-extern int git_filters_apply(git_buf *dest, git_buf *source, git_vector *filters);
+extern int git_filter_list_apply(
+	git_buf *dest,
+	git_buf *source,
+	git_filter_list *filters);
 
 /*
- * Free the `filters` array generated by `git_filters_load`.
+ * Free the git_filter_list
  *
- * Note that this frees both the array and its contents. The array will
- * be clean/reusable after this call.
- *
- * @param filters A filters array as supplied by `git_filters_load`
+ * @param filters A git_filter_list created by `git_filter_list_load`
  */
-extern void git_filters_free(git_vector *filters);
+extern void git_filter_list_free(git_filter_list *filters);
 
 /*
  * Available filters
  */
 
-/* Strip CRLF, from Worktree to ODB */
-extern int git_filter_add__crlf_to_odb(git_vector *filters, git_repository *repo, const char *path);
-
-/* Add CRLF, from ODB to worktree */
-extern int git_filter_add__crlf_to_workdir(git_vector *filters, git_repository *repo, const char *path);
+extern git_filter *git_crlf_filter_new(void);
 
 #endif
diff --git a/src/odb.c b/src/odb.c
index a0bfec4..d9310a9 100644
--- a/src/odb.c
+++ b/src/odb.c
@@ -179,13 +179,13 @@ done:
 }
 
 int git_odb__hashfd_filtered(
-	git_oid *out, git_file fd, size_t size, git_otype type, git_vector *filters)
+	git_oid *out, git_file fd, size_t size, git_otype type, git_filter_list *fl)
 {
 	int error;
 	git_buf raw = GIT_BUF_INIT;
 	git_buf filtered = GIT_BUF_INIT;
 
-	if (!filters || !filters->length)
+	if (!fl)
 		return git_odb__hashfd(out, fd, size, type);
 
 	/* size of data is used in header, so we have to read the whole file
@@ -193,7 +193,7 @@ int git_odb__hashfd_filtered(
 	 */
 
 	if (!(error = git_futils_readbuffer_fd(&raw, fd, size)))
-		error = git_filters_apply(&filtered, &raw, filters);
+		error = git_filter_list_apply(&filtered, &raw, fl);
 
 	git_buf_free(&raw);
 
diff --git a/src/odb.h b/src/odb.h
index 0d9f9e2..61dd9a7 100644
--- a/src/odb.h
+++ b/src/odb.h
@@ -14,6 +14,7 @@
 #include "vector.h"
 #include "cache.h"
 #include "posix.h"
+#include "filter.h"
 
 #define GIT_OBJECTS_DIR "objects/"
 #define GIT_OBJECT_DIR_MODE 0777
@@ -66,7 +67,7 @@ int git_odb__hashfd(git_oid *out, git_file fd, size_t size, git_otype type);
  * Acts just like git_odb__hashfd with the addition of filters...
  */
 int git_odb__hashfd_filtered(
-	git_oid *out, git_file fd, size_t len, git_otype type, git_vector *filters);
+	git_oid *out, git_file fd, size_t len, git_otype type, git_filter_list *fl);
 
 /*
  * Hash a `path`, assuming it could be a POSIX symlink: if the path is a
diff --git a/src/repository.c b/src/repository.c
index eead412..94700e4 100644
--- a/src/repository.c
+++ b/src/repository.c
@@ -1649,7 +1649,7 @@ int git_repository_hashfile(
 	const char *as_path)
 {
 	int error;
-	git_vector filters = GIT_VECTOR_INIT;
+	git_filter_list *fl = NULL;
 	git_file fd = -1;
 	git_off_t len;
 	git_buf full_path = GIT_BUF_INIT;
@@ -1671,7 +1671,7 @@ int git_repository_hashfile(
 
 	/* passing empty string for "as_path" indicated --no-filters */
 	if (strlen(as_path) > 0) {
-		error = git_filters_load(&filters, repo, as_path, GIT_FILTER_TO_ODB);
+		error = git_filter_list_load(&fl, repo, as_path, GIT_FILTER_TO_ODB);
 		if (error < 0)
 			return error;
 	} else {
@@ -1698,12 +1698,12 @@ int git_repository_hashfile(
 		goto cleanup;
 	}
 
-	error = git_odb__hashfd_filtered(out, fd, (size_t)len, type, &filters);
+	error = git_odb__hashfd_filtered(out, fd, (size_t)len, type, fl);
 
 cleanup:
 	if (fd >= 0)
 		p_close(fd);
-	git_filters_free(&filters);
+	git_filter_list_free(fl);
 	git_buf_free(&full_path);
 
 	return error;
diff --git a/tests-clar/object/blob/filter.c b/tests-clar/object/blob/filter.c
index 2b3954d..33ebedc 100644
--- a/tests-clar/object/blob/filter.c
+++ b/tests-clar/object/blob/filter.c
@@ -101,7 +101,7 @@ void test_object_blob_filter__stats(void)
 
 void test_object_blob_filter__to_odb(void)
 {
-	git_vector filters = GIT_VECTOR_INIT;
+	git_filter_list *fl = NULL;
 	git_config *cfg;
 	int i;
 	git_blob *blob;
@@ -113,21 +113,21 @@ void test_object_blob_filter__to_odb(void)
 	git_attr_cache_flush(g_repo);
 	cl_git_append2file("empty_standard_repo/.gitattributes", "*.txt text\n");
 
-	cl_assert(git_filters_load(
-		&filters, g_repo, "filename.txt", GIT_FILTER_TO_ODB) > 0);
-	cl_assert(filters.length == 1);
+	cl_git_pass(
+		git_filter_list_load(&fl, g_repo, "filename.txt", GIT_FILTER_TO_ODB));
+	cl_assert(fl != NULL);
 
 	for (i = 0; i < NUM_TEST_OBJECTS; i++) {
 		cl_git_pass(git_blob_lookup(&blob, g_repo, &g_oids[i]));
 		cl_git_pass(git_blob__getbuf(&orig, blob));
 
-		cl_git_pass(git_filters_apply(&out, &orig, &filters));
+		cl_git_pass(git_filter_list_apply(&out, &orig, fl));
 		cl_assert(git_buf_cmp(&out, &g_crlf_filtered[i]) == 0);
 
 		git_blob_free(blob);
 	}
 
-	git_filters_free(&filters);
+	git_filter_list_free(fl);
 	git_buf_free(&orig);
 	git_buf_free(&out);
 	git_config_free(cfg);