Add git_config_refresh() API to reload config

This adds a new API that allows users to reload the config if the
file has changed on disk.  A new config callback function to
refresh the config was added.

The modified time and file size are used to test if the file needs
to be reloaded (and are now stored in the disk backend object).

In writing tests, just using mtime was a problem / race, so I
wanted to check file size as well.  To support that, I extended
`git_futils_readbuffer_updated` to optionally check file size in
addition to mtime, and I added a new function `git_filebuf_stats`
to fetch the mtime and size for an open filebuf (so that the
config could be easily refreshed after a write).

Lastly, I moved some similar file checking code for attributes
into filebuf.  It is still only being used for attrs, but it
seems potentially reusable, so I thought I'd move it over.

include/git2/config.h

@@ -56,6 +56,7 @@ struct git_config_file {
 	int (*set_multivar)(git_config_file *cfg, const char *name, const char *regexp, const char *value);
 	int (*del)(struct git_config_file *, const char *key);
 	int (*foreach)(struct git_config_file *, const char *, int (*fn)(const git_config_entry *, void *), void *data);
+	int (*refresh)(struct git_config_file *);
 	void (*free)(struct git_config_file *);
 };
 
@@ -243,6 +244,19 @@ GIT_EXTERN(int) git_config_open_level(
     unsigned int level);
 
 /**
+ * Reload changed config files
+ *
+ * A config file may be changed on disk out from under the in-memory
+ * config object.  This function causes us to look for files that have
+ * been modified since we last loaded them and refresh the config with
+ * the latest information.
+ *
+ * @param cfg The configuration to refresh
+ * @return 0 or an error code
+ */
+GIT_EXTERN(int) git_config_refresh(git_config *cfg);
+
+/**
  * Free the configuration and its associated memory and files
  *
  * @param cfg the configuration to free

src/attr.c

@@ -261,32 +261,26 @@ bool git_attr_cache__is_cached(
 
 static int load_attr_file(
 	const char **data,
-	git_attr_file_stat_sig *sig,
+	git_futils_stat_sig *sig,
 	const char *filename)
 {
 	int error;
 	git_buf content = GIT_BUF_INIT;
-	struct stat st;
 
-	if (p_stat(filename, &st) < 0)
-		return GIT_ENOTFOUND;
+	error = git_futils_stat_sig_needs_reload(sig, filename);
+	if (error < 0)
+		return error;
 
-	if (sig != NULL &&
-		(git_time_t)st.st_mtime == sig->seconds &&
-		(git_off_t)st.st_size == sig->size &&
-		(unsigned int)st.st_ino == sig->ino)
+	/* if error == 0, then file is up to date. By returning GIT_ENOTFOUND,
+	 * we tell the caller not to reparse this file...
+	 */
+	if (!error)
 		return GIT_ENOTFOUND;
 
-	error = git_futils_readbuffer_updated(&content, filename, NULL, NULL);
+	error = git_futils_readbuffer(&content, filename);
 	if (error < 0)
 		return error;
 
-	if (sig != NULL) {
-		sig->seconds = (git_time_t)st.st_mtime;
-		sig->size    = (git_off_t)st.st_size;
-		sig->ino     = (unsigned int)st.st_ino;
-	}
-
 	*data = git_buf_detach(&content);
 
 	return 0;
@@ -386,7 +380,7 @@ int git_attr_cache__push_file(
 	git_attr_cache *cache = git_repository_attr_cache(repo);
 	git_attr_file *file = NULL;
 	git_blob *blob = NULL;
-	git_attr_file_stat_sig st;
+	git_futils_stat_sig sig;
 
 	assert(filename && stack);
 
@@ -409,11 +403,11 @@ int git_attr_cache__push_file(
 
 	if (source == GIT_ATTR_FILE_FROM_FILE) {
 		if (file)
-			memcpy(&st, &file->cache_data.st, sizeof(st));
+			memcpy(&sig, &file->cache_data.sig, sizeof(sig));
 		else
-			memset(&st, 0, sizeof(st));
+			memset(&sig, 0, sizeof(sig));
 
-		error = load_attr_file(&content, &st, filename);
+		error = load_attr_file(&content, &sig, filename);
 	} else {
 		error = load_attr_blob_from_index(&content, &blob,
 			repo, file ? &file->cache_data.oid : NULL, relfile);
@@ -448,7 +442,7 @@ int git_attr_cache__push_file(
 	if (blob)
 		git_oid_cpy(&file->cache_data.oid, git_object_id((git_object *)blob));
 	else
-		memcpy(&file->cache_data.st, &st, sizeof(st));
+		memcpy(&file->cache_data.sig, &sig, sizeof(sig));
 
 finish:
 	/* push file onto vector if we found one*/

src/attr_file.h

@@ -11,6 +11,7 @@
 #include "vector.h"
 #include "pool.h"
 #include "buffer.h"
+#include "fileops.h"
 
 #define GIT_ATTR_FILE			".gitattributes"
 #define GIT_ATTR_FILE_INREPO	"info/attributes"
@@ -54,19 +55,13 @@ typedef struct {
 } git_attr_assignment;
 
 typedef struct {
-	git_time_t seconds;
-	git_off_t  size;
-	unsigned int ino;
-} git_attr_file_stat_sig;
-
-typedef struct {
 	char *key;				/* cache "source#path" this was loaded from */
 	git_vector rules;		/* vector of <rule*> or <fnmatch*> */
 	git_pool *pool;
 	bool pool_is_allocated;
 	union {
 		git_oid oid;
-		git_attr_file_stat_sig st;
+		git_futils_stat_sig sig;
 	} cache_data;
 } git_attr_file;
 

src/config.c

@@ -267,6 +267,20 @@ int git_config_add_file(
 	return 0;
 }
 
+int git_config_refresh(git_config *cfg)
+{
+	int error = 0;
+	unsigned int i;
+
+	for (i = 0; i < cfg->files.length && !error; ++i) {
+		file_internal *internal = git_vector_get(&cfg->files, i);
+		git_config_file *file = internal->file;
+		error = file->refresh(file);
+	}
+
+	return error;
+}
+
 /*
  * Loop over all the variables
  */

src/config_file.c

@@ -75,7 +75,11 @@ typedef struct {
 		int eof;
 	} reader;
 
-	char *file_path;
+	char  *file_path;
+	time_t file_mtime;
+	size_t file_size;
+
+	unsigned int level;
 } diskfile_backend;
 
 static int config_parse(diskfile_backend *cfg_file, unsigned int level);
@@ -150,25 +154,53 @@ static int config_open(git_config_file *cfg, unsigned int level)
 	int res;
 	diskfile_backend *b = (diskfile_backend *)cfg;
 
+	b->level = level;
+
 	b->values = git_strmap_alloc();
 	GITERR_CHECK_ALLOC(b->values);
 
 	git_buf_init(&b->reader.buffer, 0);
-	res = git_futils_readbuffer(&b->reader.buffer, b->file_path);
+	res = git_futils_readbuffer_updated(
+		&b->reader.buffer, b->file_path, &b->file_mtime, &b->file_size, NULL);
 
 	/* It's fine if the file doesn't exist */
 	if (res == GIT_ENOTFOUND)
 		return 0;
 
-	if (res < 0 || config_parse(b, level) <  0) {
+	if (res < 0 || (res = config_parse(b, level)) < 0) {
 		free_vars(b->values);
 		b->values = NULL;
-		git_buf_free(&b->reader.buffer);
-		return -1;
 	}
 
 	git_buf_free(&b->reader.buffer);
-	return 0;
+	return res;
+}
+
+static int config_refresh(git_config_file *cfg)
+{
+	int res, updated = 0;
+	diskfile_backend *b = (diskfile_backend *)cfg;
+	git_strmap *old_values;
+
+	res = git_futils_readbuffer_updated(
+		&b->reader.buffer, b->file_path, &b->file_mtime, &b->file_size, &updated);
+	if (res < 0 || !updated)
+		return (res == GIT_ENOTFOUND) ? 0 : res;
+
+	/* need to reload - store old values and prep for reload */
+	old_values = b->values;
+	b->values = git_strmap_alloc();
+	GITERR_CHECK_ALLOC(b->values);
+
+	if ((res = config_parse(b, b->level)) < 0) {
+		free_vars(b->values);
+		b->values = old_values;
+	} else {
+		free_vars(old_values);
+	}
+
+	git_buf_free(&b->reader.buffer);
+	return res;
 }
 
 static void backend_free(git_config_file *_backend)
@@ -527,6 +559,7 @@ int git_config_file__ondisk(git_config_file **out, const char *path)
 	backend->parent.set_multivar = config_set_multivar;
 	backend->parent.del = config_delete;
 	backend->parent.foreach = file_foreach;
+	backend->parent.refresh = config_refresh;
 	backend->parent.free = backend_free;
 
 	*out = (git_config_file *)backend;
@@ -1197,8 +1230,12 @@ static int config_write(diskfile_backend *cfg, const char *key, const regex_t *p
 	git__free(section);
 	git__free(current_section);
 
+	/* refresh stats - if this errors, then commit will error too */
+	(void)git_filebuf_stats(&cfg->file_mtime, &cfg->file_size, &file);
+
 	result = git_filebuf_commit(&file, GIT_CONFIG_FILE_MODE);
 	git_buf_free(&cfg->reader.buffer);
+
 	return result;
 
 rewrite_fail:

src/filebuf.c

@@ -466,3 +466,26 @@ int git_filebuf_printf(git_filebuf *file, const char *format, ...)
 	return res;
 }
 
+int git_filebuf_stats(time_t *mtime, size_t *size, git_filebuf *file)
+{
+	int res;
+	struct stat st;
+
+	if (file->fd_is_open)
+		res = p_fstat(file->fd, &st);
+	else
+		res = p_stat(file->path_original, &st);
+
+	if (res < 0) {
+		giterr_set(GITERR_OS, "Could not get stat info for '%s'",
+			file->path_original);
+		return res;
+	}
+
+	if (mtime)
+		*mtime = st.st_mtime;
+	if (size)
+		*size = (size_t)st.st_size;
+
+	return 0;
+}

src/filebuf.h

@@ -82,5 +82,6 @@ int git_filebuf_commit_at(git_filebuf *lock, const char *path, mode_t mode);
 void git_filebuf_cleanup(git_filebuf *lock);
 int git_filebuf_hash(git_oid *oid, git_filebuf *file);
 int git_filebuf_flush(git_filebuf *file);
+int git_filebuf_stats(time_t *mtime, size_t *size, git_filebuf *file);
 
 #endif

src/fileops.c

@@ -142,10 +142,11 @@ int git_futils_readbuffer_fd(git_buf *buf, git_file fd, size_t len)
 }
 
 int git_futils_readbuffer_updated(
-	git_buf *buf, const char *path, time_t *mtime, int *updated)
+	git_buf *buf, const char *path, time_t *mtime, size_t *size, int *updated)
 {
 	git_file fd;
 	struct stat st;
+	bool changed = false;
 
 	assert(buf && path && *path);
 
@@ -162,16 +163,25 @@ int git_futils_readbuffer_updated(
 	}
 
 	/*
-	 * If we were given a time, we only want to read the file if it
-	 * has been modified.
+	 * If we were given a time and/or a size, we only want to read the file
+	 * if it has been modified.
 	 */
-	if (mtime != NULL && *mtime >= st.st_mtime) {
+	if (size && *size != (size_t)st.st_size)
+		changed = true;
+	if (mtime && *mtime != st.st_mtime)
+		changed = true;
+	if (!size && !mtime)
+		changed = true;
+
+	if (!changed) {
 		p_close(fd);
 		return 0;
 	}
 
 	if (mtime != NULL)
 		*mtime = st.st_mtime;
+	if (size != NULL)
+		*size = (size_t)st.st_size;
 
 	if (git_futils_readbuffer_fd(buf, fd, (size_t)st.st_size) < 0) {
 		p_close(fd);
@@ -188,7 +198,7 @@ int git_futils_readbuffer_updated(
 
 int git_futils_readbuffer(git_buf *buf, const char *path)
 {
-	return git_futils_readbuffer_updated(buf, path, NULL, NULL);
+	return git_futils_readbuffer_updated(buf, path, NULL, NULL, NULL);
 }
 
 int git_futils_mv_withpath(const char *from, const char *to, const mode_t dirmode)
@@ -660,3 +670,28 @@ int git_futils_cp_r(
 
 	return error;
 }
+
+int git_futils_stat_sig_needs_reload(
+	git_futils_stat_sig *sig, const char *path)
+{
+	struct stat st;
+
+	/* if the sig is NULL, then alway reload */
+	if (sig == NULL)
+		return 1;
+
+	if (p_stat(path, &st) < 0)
+		return GIT_ENOTFOUND;
+
+	if ((git_time_t)st.st_mtime == sig->seconds &&
+		(git_off_t)st.st_size == sig->size &&
+		(unsigned int)st.st_ino == sig->ino)
+		return 0;
+
+	sig->seconds = (git_time_t)st.st_mtime;
+	sig->size    = (git_off_t)st.st_size;
+	sig->ino     = (unsigned int)st.st_ino;
+
+	return 1;
+}
+

src/fileops.h

@@ -18,7 +18,8 @@
  * Read whole files into an in-memory buffer for processing
  */
 extern int git_futils_readbuffer(git_buf *obj, const char *path);
-extern int git_futils_readbuffer_updated(git_buf *obj, const char *path, time_t *mtime, int *updated);
+extern int git_futils_readbuffer_updated(
+	git_buf *obj, const char *path, time_t *mtime, size_t *size, int *updated);
 extern int git_futils_readbuffer_fd(git_buf *obj, git_file fd, size_t len);
 
 /**
@@ -266,4 +267,26 @@ extern int git_futils_find_system_file(git_buf *path, const char *filename);
  */
 extern int git_futils_fake_symlink(const char *new, const char *old);
 
+
+typedef struct {
+	git_time_t seconds;
+	git_off_t  size;
+	unsigned int ino;
+} git_futils_stat_sig;
+
+/**
+ * Compare stat information for file with reference info.
+ *
+ * Use this as a way to track if a file has changed on disk.  This will
+ * return GIT_ENOTFOUND if the file doesn't exist, 0 if the file is up-to-date
+ * with regards to the signature, and 1 if the file needs to reloaded.  When
+ * a 1 is returned, the signature will also be updated with the latest data.
+ *
+ * @param sig stat signature structure
+ * @param path path to be statted
+ * @return 0 if up-to-date, 1 if out-of-date, <0 on error
+ */
+extern int git_futils_stat_sig_needs_reload(
+	git_futils_stat_sig *sig, const char *path);
+
 #endif /* INCLUDE_fileops_h__ */

src/index.c

@@ -405,7 +405,7 @@ int git_index_read(git_index *index)
 	/* We don't want to update the mtime if we fail to parse the index */
 	mtime = index->last_modified;
 	error = git_futils_readbuffer_updated(
-		&buffer, index->index_file_path, &mtime, &updated);
+		&buffer, index->index_file_path, &mtime, NULL, &updated);
 	if (error < 0)
 		return error;
 

src/refs.c

@@ -123,7 +123,8 @@ static int reference_read(
 	if (git_buf_joinpath(&path, repo_path, ref_name) < 0)
 		return -1;
 
-	result = git_futils_readbuffer_updated(file_content, path.ptr, mtime, updated);
+	result = git_futils_readbuffer_updated(
+		file_content, path.ptr, mtime, NULL, updated);
 	git_buf_free(&path);
 
 	return result;

tests-clar/config/refresh.c

+#include "clar_libgit2.h"
+
+#define TEST_FILE "config.refresh"
+
+void test_config_refresh__initialize(void)
+{
+}
+
+void test_config_refresh__cleanup(void)
+{
+	cl_fixture_cleanup(TEST_FILE);
+}
+
+void test_config_refresh__update_value(void)
+{
+	git_config *cfg;
+	int32_t v;
+
+	cl_git_mkfile(TEST_FILE, "[section]\n\tvalue = 1\n\n");
+
+	/* By freeing the config, we make sure we flush the values  */
+	cl_git_pass(git_config_open_ondisk(&cfg, TEST_FILE));
+
+	cl_git_pass(git_config_get_int32(&v, cfg, "section.value"));
+	cl_assert_equal_i(1, v);
+
+	cl_git_rewritefile(TEST_FILE, "[section]\n\tvalue = 10\n\n");
+
+	cl_git_pass(git_config_get_int32(&v, cfg, "section.value"));
+	cl_assert_equal_i(1, v);
+
+	cl_git_pass(git_config_refresh(cfg));
+
+	cl_git_pass(git_config_get_int32(&v, cfg, "section.value"));
+	cl_assert_equal_i(10, v);
+
+	git_config_free(cfg);
+}
+
+void test_config_refresh__delete_value(void)
+{
+	git_config *cfg;
+	int32_t v;
+
+	cl_git_mkfile(TEST_FILE, "[section]\n\tvalue = 1\n\n");
+
+	/* By freeing the config, we make sure we flush the values  */
+	cl_git_pass(git_config_open_ondisk(&cfg, TEST_FILE));
+
+	cl_git_pass(git_config_get_int32(&v, cfg, "section.value"));
+	cl_assert_equal_i(1, v);
+	cl_git_fail(git_config_get_int32(&v, cfg, "section.newval"));
+
+	cl_git_rewritefile(TEST_FILE, "[section]\n\tnewval = 10\n\n");
+
+	cl_git_pass(git_config_get_int32(&v, cfg, "section.value"));
+	cl_assert_equal_i(1, v);
+	cl_git_fail(git_config_get_int32(&v, cfg, "section.newval"));
+
+	cl_git_pass(git_config_refresh(cfg));
+
+	cl_git_fail(git_config_get_int32(&v, cfg, "section.value"));
+	cl_git_pass(git_config_get_int32(&v, cfg, "section.newval"));
+	cl_assert_equal_i(10, v);
+
+	git_config_free(cfg);
+}