thodg/libgit2/src/config_file.c

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• Hash : afca16a7
  Author :
  Date : 2022-01-22T13:14:59
  

  config: use a byte array for checksum

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• src/config_file.c

• /*
   * 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 "config.h"
  
  #include "git2/config.h"
  #include "git2/sys/config.h"
  
  #include "array.h"
  #include "str.h"
  #include "config_backend.h"
  #include "config_entries.h"
  #include "config_parse.h"
  #include "filebuf.h"
  #include "regexp.h"
  #include "sysdir.h"
  #include "wildmatch.h"
  #include "hash.h"
  
  /* Max depth for [include] directives */
  #define MAX_INCLUDE_DEPTH 10
  
  typedef struct config_file {
  	git_futils_filestamp stamp;
  	unsigned char checksum[GIT_HASH_SHA1_SIZE];
  	char *path;
  	git_array_t(struct config_file) includes;
  } config_file;
  
  typedef struct {
  	git_config_backend parent;
  	git_mutex values_mutex;
  	git_config_entries *entries;
  	const git_repository *repo;
  	git_config_level_t level;
  
  	git_array_t(git_config_parser) readers;
  
  	bool locked;
  	git_filebuf locked_buf;
  	git_str locked_content;
  
  	config_file file;
  } config_file_backend;
  
  typedef struct {
  	const git_repository *repo;
  	config_file *file;
  	git_config_entries *entries;
  	git_config_level_t level;
  	unsigned int depth;
  } config_file_parse_data;
  
  static int config_file_read(git_config_entries *entries, const git_repository *repo, config_file *file, git_config_level_t level, int depth);
  static int config_file_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_file_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);
  
  /**
   * Take the current values map from the backend and increase its
   * refcount. This is its own function to make sure we use the mutex to
   * avoid the map pointer from changing under us.
   */
  static int config_file_entries_take(git_config_entries **out, config_file_backend *b)
  {
  	int error;
  
  	if ((error = git_mutex_lock(&b->values_mutex)) < 0) {
  		git_error_set(GIT_ERROR_OS, "failed to lock config backend");
  		return error;
  	}
  
  	git_config_entries_incref(b->entries);
  	*out = b->entries;
  
  	git_mutex_unlock(&b->values_mutex);
  
  	return 0;
  }
  
  static void config_file_clear(config_file *file)
  {
  	config_file *include;
  	uint32_t i;
  
  	if (file == NULL)
  		return;
  
  	git_array_foreach(file->includes, i, include) {
  		config_file_clear(include);
  	}
  	git_array_clear(file->includes);
  
  	git__free(file->path);
  }
  
  static int config_file_open(git_config_backend *cfg, git_config_level_t level, const git_repository *repo)
  {
  	config_file_backend *b = GIT_CONTAINER_OF(cfg, config_file_backend, parent);
  	int res;
  
  	b->level = level;
  	b->repo = repo;
  
  	if ((res = git_config_entries_new(&b->entries)) < 0)
  		return res;
  
  	if (!git_fs_path_exists(b->file.path))
  		return 0;
  
  	/*
  	 * git silently ignores configuration files that are not
  	 * readable.  We emulate that behavior.  This is particularly
  	 * important for sandboxed applications on macOS where the
  	 * git configuration files may not be readable.
  	 */
  	if (p_access(b->file.path, R_OK) < 0)
  		return GIT_ENOTFOUND;
  
  	if (res < 0 || (res = config_file_read(b->entries, repo, &b->file, level, 0)) < 0) {
  		git_config_entries_free(b->entries);
  		b->entries = NULL;
  	}
  
  	return res;
  }
  
  static int config_file_is_modified(int *modified, config_file *file)
  {
  	config_file *include;
  	git_str buf = GIT_STR_INIT;
  	unsigned char checksum[GIT_HASH_SHA1_SIZE];
  	uint32_t i;
  	int error = 0;
  
  	*modified = 0;
  
  	if (!git_futils_filestamp_check(&file->stamp, file->path))
  		goto check_includes;
  
  	if ((error = git_futils_readbuffer(&buf, file->path)) < 0)
  		goto out;
  
  	if ((error = git_hash_buf(checksum, buf.ptr, buf.size, GIT_HASH_ALGORITHM_SHA1)) < 0)
  		goto out;
  
  	if (memcmp(checksum, file->checksum, GIT_HASH_SHA1_SIZE) != 0) {
  		*modified = 1;
  		goto out;
  	}
  
  check_includes:
  	git_array_foreach(file->includes, i, include) {
  		if ((error = config_file_is_modified(modified, include)) < 0 || *modified)
  			goto out;
  	}
  
  out:
  	git_str_dispose(&buf);
  
  	return error;
  }
  
  static void config_file_clear_includes(config_file_backend *cfg)
  {
  	config_file *include;
  	uint32_t i;
  
  	git_array_foreach(cfg->file.includes, i, include)
  		config_file_clear(include);
  	git_array_clear(cfg->file.includes);
  }
  
  static int config_file_set_entries(git_config_backend *cfg, git_config_entries *entries)
  {
  	config_file_backend *b = GIT_CONTAINER_OF(cfg, config_file_backend, parent);
  	git_config_entries *old = NULL;
  	int error;
  
  	if (b->parent.readonly) {
  		git_error_set(GIT_ERROR_CONFIG, "this backend is read-only");
  		return -1;
  	}
  
  	if ((error = git_mutex_lock(&b->values_mutex)) < 0) {
  		git_error_set(GIT_ERROR_OS, "failed to lock config backend");
  		goto out;
  	}
  
  	old = b->entries;
  	b->entries = entries;
  
  	git_mutex_unlock(&b->values_mutex);
  
  out:
  	git_config_entries_free(old);
  	return error;
  }
  
  static int config_file_refresh_from_buffer(git_config_backend *cfg, const char *buf, size_t buflen)
  {
  	config_file_backend *b = GIT_CONTAINER_OF(cfg, config_file_backend, parent);
  	git_config_entries *entries = NULL;
  	int error;
  
  	config_file_clear_includes(b);
  
  	if ((error = git_config_entries_new(&entries)) < 0 ||
  	    (error = config_file_read_buffer(entries, b->repo, &b->file,
  					     b->level, 0, buf, buflen)) < 0 ||
  	    (error = config_file_set_entries(cfg, entries)) < 0)
  		goto out;
  
  	entries = NULL;
  out:
  	git_config_entries_free(entries);
  	return error;
  }
  
  static int config_file_refresh(git_config_backend *cfg)
  {
  	config_file_backend *b = GIT_CONTAINER_OF(cfg, config_file_backend, parent);
  	git_config_entries *entries = NULL;
  	int error, modified;
  
  	if (cfg->readonly)
  		return 0;
  
  	if ((error = config_file_is_modified(&modified, &b->file)) < 0 && error != GIT_ENOTFOUND)
  		goto out;
  
  	if (!modified)
  		return 0;
  
  	config_file_clear_includes(b);
  
  	if ((error = git_config_entries_new(&entries)) < 0 ||
  	    (error = config_file_read(entries, b->repo, &b->file, b->level, 0)) < 0 ||
  	    (error = config_file_set_entries(cfg, entries)) < 0)
  		goto out;
  
  	entries = NULL;
  out:
  	git_config_entries_free(entries);
  
  	return (error == GIT_ENOTFOUND) ? 0 : error;
  }
  
  static void config_file_free(git_config_backend *_backend)
  {
  	config_file_backend *backend = GIT_CONTAINER_OF(_backend, config_file_backend, parent);
  
  	if (backend == NULL)
  		return;
  
  	config_file_clear(&backend->file);
  	git_config_entries_free(backend->entries);
  	git_mutex_free(&backend->values_mutex);
  	git__free(backend);
  }
  
  static int config_file_iterator(
  	git_config_iterator **iter,
  	struct git_config_backend *backend)
  {
  	config_file_backend *b = GIT_CONTAINER_OF(backend, config_file_backend, parent);
  	git_config_entries *dupped = NULL, *entries = NULL;
  	int error;
  
  	if ((error = config_file_refresh(backend)) < 0 ||
  	    (error = config_file_entries_take(&entries, b)) < 0 ||
  	    (error = git_config_entries_dup(&dupped, entries)) < 0 ||
  	    (error = git_config_entries_iterator_new(iter, dupped)) < 0)
  		goto out;
  
  out:
  	/* Let iterator delete duplicated entries when it's done */
  	git_config_entries_free(entries);
  	git_config_entries_free(dupped);
  	return error;
  }
  
  static int config_file_snapshot(git_config_backend **out, git_config_backend *backend)
  {
  	return git_config_backend_snapshot(out, backend);
  }
  
  static int config_file_set(git_config_backend *cfg, const char *name, const char *value)
  {
  	config_file_backend *b = GIT_CONTAINER_OF(cfg, config_file_backend, parent);
  	git_config_entries *entries;
  	git_config_entry *existing;
  	char *key, *esc_value = NULL;
  	int error;
  
  	if ((error = git_config__normalize_name(name, &key)) < 0)
  		return error;
  
  	if ((error = config_file_entries_take(&entries, b)) < 0)
  		return error;
  
  	/* Check whether we'd be modifying an included or multivar key */
  	if ((error = git_config_entries_get_unique(&existing, entries, key)) < 0) {
  		if (error != GIT_ENOTFOUND)
  			goto out;
  		error = 0;
  	} else if ((!existing->value && !value) ||
  		   (existing->value && value && !strcmp(existing->value, value))) {
  		/* don't update if old and new values already match */
  		error = 0;
  		goto out;
  	}
  
  	/* No early returns due to sanity checks, let's write it out and refresh */
  	if (value) {
  		esc_value = escape_value(value);
  		GIT_ERROR_CHECK_ALLOC(esc_value);
  	}
  
  	if ((error = config_file_write(b, name, key, NULL, esc_value)) < 0)
  		goto out;
  
  out:
  	git_config_entries_free(entries);
  	git__free(esc_value);
  	git__free(key);
  	return error;
  }
  
  /* release the map containing the entry as an equivalent to freeing it */
  static void config_file_entry_free(git_config_entry *entry)
  {
  	git_config_entries *entries = (git_config_entries *) entry->payload;
  	git_config_entries_free(entries);
  }
  
  /*
   * Internal function that actually gets the value in string form
   */
  static int config_file_get(git_config_backend *cfg, const char *key, git_config_entry **out)
  {
  	config_file_backend *h = GIT_CONTAINER_OF(cfg, config_file_backend, parent);
  	git_config_entries *entries = NULL;
  	git_config_entry *entry;
  	int error = 0;
  
  	if (!h->parent.readonly && ((error = config_file_refresh(cfg)) < 0))
  		return error;
  
  	if ((error = config_file_entries_take(&entries, h)) < 0)
  		return error;
  
  	if ((error = (git_config_entries_get(&entry, entries, key))) < 0) {
  		git_config_entries_free(entries);
  		return error;
  	}
  
  	entry->free = config_file_entry_free;
  	entry->payload = entries;
  	*out = entry;
  
  	return 0;
  }
  
  static int config_file_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);
  	git_regexp preg;
  	int result;
  	char *key;
  
  	GIT_ASSERT_ARG(regexp);
  
  	if ((result = git_config__normalize_name(name, &key)) < 0)
  		return result;
  
  	if ((result = git_regexp_compile(&preg, regexp, 0)) < 0)
  		goto out;
  
  	/* If we do have it, set call config_file_write() and reload */
  	if ((result = config_file_write(b, name, key, &preg, value)) < 0)
  		goto out;
  
  out:
  	git__free(key);
  	git_regexp_dispose(&preg);
  
  	return result;
  }
  
  static int config_file_delete(git_config_backend *cfg, const char *name)
  {
  	config_file_backend *b = GIT_CONTAINER_OF(cfg, config_file_backend, parent);
  	git_config_entries *entries = NULL;
  	git_config_entry *entry;
  	char *key = NULL;
  	int error;
  
  	if ((error = git_config__normalize_name(name, &key)) < 0)
  		goto out;
  
  	if ((error = config_file_entries_take(&entries, b)) < 0)
  		goto out;
  
  	/* Check whether we'd be modifying an included or multivar key */
  	if ((error = git_config_entries_get_unique(&entry, entries, key)) < 0) {
  		if (error == GIT_ENOTFOUND)
  			git_error_set(GIT_ERROR_CONFIG, "could not find key '%s' to delete", name);
  		goto out;
  	}
  
  	if ((error = config_file_write(b, name, entry->name, NULL, NULL)) < 0)
  		goto out;
  
  out:
  	git_config_entries_free(entries);
  	git__free(key);
  	return error;
  }
  
  static int config_file_delete_multivar(git_config_backend *cfg, const char *name, const char *regexp)
  {
  	config_file_backend *b = GIT_CONTAINER_OF(cfg, config_file_backend, parent);
  	git_config_entries *entries = NULL;
  	git_config_entry *entry = NULL;
  	git_regexp preg = GIT_REGEX_INIT;
  	char *key = NULL;
  	int result;
  
  	if ((result = git_config__normalize_name(name, &key)) < 0)
  		goto out;
  
  	if ((result = config_file_entries_take(&entries, b)) < 0)
  		goto out;
  
  	if ((result = git_config_entries_get(&entry, entries, key)) < 0) {
  		if (result == GIT_ENOTFOUND)
  			git_error_set(GIT_ERROR_CONFIG, "could not find key '%s' to delete", name);
  		goto out;
  	}
  
  	if ((result = git_regexp_compile(&preg, regexp, 0)) < 0)
  		goto out;
  
  	if ((result = config_file_write(b, name, key, &preg, NULL)) < 0)
  		goto out;
  
  out:
  	git_config_entries_free(entries);
  	git__free(key);
  	git_regexp_dispose(&preg);
  	return result;
  }
  
  static int config_file_lock(git_config_backend *_cfg)
  {
  	config_file_backend *cfg = GIT_CONTAINER_OF(_cfg, config_file_backend, parent);
  	int error;
  
  	if ((error = git_filebuf_open(&cfg->locked_buf, cfg->file.path, 0, GIT_CONFIG_FILE_MODE)) < 0)
  		return error;
  
  	error = git_futils_readbuffer(&cfg->locked_content, cfg->file.path);
  	if (error < 0 && error != GIT_ENOTFOUND) {
  		git_filebuf_cleanup(&cfg->locked_buf);
  		return error;
  	}
  
  	cfg->locked = true;
  	return 0;
  
  }
  
  static int config_file_unlock(git_config_backend *_cfg, int success)
  {
  	config_file_backend *cfg = GIT_CONTAINER_OF(_cfg, config_file_backend, parent);
  	int error = 0;
  
  	if (success) {
  		git_filebuf_write(&cfg->locked_buf, cfg->locked_content.ptr, cfg->locked_content.size);
  		error = git_filebuf_commit(&cfg->locked_buf);
  	}
  
  	git_filebuf_cleanup(&cfg->locked_buf);
  	git_str_dispose(&cfg->locked_content);
  	cfg->locked = false;
  
  	return error;
  }
  
  int git_config_backend_from_file(git_config_backend **out, const char *path)
  {
  	config_file_backend *backend;
  
  	backend = git__calloc(1, sizeof(config_file_backend));
  	GIT_ERROR_CHECK_ALLOC(backend);
  
  	backend->parent.version = GIT_CONFIG_BACKEND_VERSION;
  	git_mutex_init(&backend->values_mutex);
  
  	backend->file.path = git__strdup(path);
  	GIT_ERROR_CHECK_ALLOC(backend->file.path);
  	git_array_init(backend->file.includes);
  
  	backend->parent.open = config_file_open;
  	backend->parent.get = config_file_get;
  	backend->parent.set = config_file_set;
  	backend->parent.set_multivar = config_file_set_multivar;
  	backend->parent.del = config_file_delete;
  	backend->parent.del_multivar = config_file_delete_multivar;
  	backend->parent.iterator = config_file_iterator;
  	backend->parent.snapshot = config_file_snapshot;
  	backend->parent.lock = config_file_lock;
  	backend->parent.unlock = config_file_unlock;
  	backend->parent.free = config_file_free;
  
  	*out = (git_config_backend *)backend;
  
  	return 0;
  }
  
  static int included_path(git_str *out, const char *dir, const char *path)
  {
  	/* From the user's home */
  	if (path[0] == '~' && path[1] == '/')
  		return git_sysdir_expand_global_file(out, &path[1]);
  
  	return git_fs_path_join_unrooted(out, path, dir, NULL);
  }
  
  /* Escape the values to write them to the file */
  static char *escape_value(const char *ptr)
  {
  	git_str buf;
  	size_t len;
  	const char *esc;
  
  	GIT_ASSERT_ARG_WITH_RETVAL(ptr, NULL);
  
  	len = strlen(ptr);
  	if (!len)
  		return git__calloc(1, sizeof(char));
  
  	if (git_str_init(&buf, len) < 0)
  		return NULL;
  
  	while (*ptr != '\0') {
  		if ((esc = strchr(git_config_escaped, *ptr)) != NULL) {
  			git_str_putc(&buf, '\\');
  			git_str_putc(&buf, git_config_escapes[esc - git_config_escaped]);
  		} else {
  			git_str_putc(&buf, *ptr);
  		}
  		ptr++;
  	}
  
  	if (git_str_oom(&buf))
  		return NULL;
  
  	return git_str_detach(&buf);
  }
  
  static int parse_include(config_file_parse_data *parse_data, const char *file)
  {
  	config_file *include;
  	git_str path = GIT_STR_INIT;
  	char *dir;
  	int result;
  
  	if (!file)
  		return 0;
  
  	if ((result = git_fs_path_dirname_r(&path, parse_data->file->path)) < 0)
  		return result;
  
  	dir = git_str_detach(&path);
  	result = included_path(&path, dir, file);
  	git__free(dir);
  
  	if (result < 0)
  		return result;
  
  	include = git_array_alloc(parse_data->file->includes);
  	GIT_ERROR_CHECK_ALLOC(include);
  	memset(include, 0, sizeof(*include));
  	git_array_init(include->includes);
  	include->path = git_str_detach(&path);
  
  	result = config_file_read(parse_data->entries, parse_data->repo, include,
  				  parse_data->level, parse_data->depth+1);
  
  	if (result == GIT_ENOTFOUND) {
  		git_error_clear();
  		result = 0;
  	}
  
  	return result;
  }
  
  static int do_match_gitdir(
  	int *matches,
  	const git_repository *repo,
  	const char *cfg_file,
  	const char *condition,
  	bool case_insensitive)
  {
  	git_str pattern = GIT_STR_INIT, gitdir = GIT_STR_INIT;
  	int error;
  
  	if (condition[0] == '.' && git_fs_path_is_dirsep(condition[1])) {
  		git_fs_path_dirname_r(&pattern, cfg_file);
  		git_str_joinpath(&pattern, pattern.ptr, condition + 2);
  	} else if (condition[0] == '~' && git_fs_path_is_dirsep(condition[1]))
  		git_sysdir_expand_global_file(&pattern, condition + 1);
  	else if (!git_fs_path_is_absolute(condition))
  		git_str_joinpath(&pattern, "**", condition);
  	else
  		git_str_sets(&pattern, condition);
  
  	if (git_fs_path_is_dirsep(condition[strlen(condition) - 1]))
  		git_str_puts(&pattern, "**");
  
  	if (git_str_oom(&pattern)) {
  		error = -1;
  		goto out;
  	}
  
  	if ((error = git_repository__item_path(&gitdir, repo, GIT_REPOSITORY_ITEM_GITDIR)) < 0)
  		goto out;
  
  	if (git_fs_path_is_dirsep(gitdir.ptr[gitdir.size - 1]))
  		git_str_truncate(&gitdir, gitdir.size - 1);
  
  	*matches = wildmatch(pattern.ptr, gitdir.ptr,
  			     WM_PATHNAME | (case_insensitive ? WM_CASEFOLD : 0)) == WM_MATCH;
  out:
  	git_str_dispose(&pattern);
  	git_str_dispose(&gitdir);
  	return error;
  }
  
  static int conditional_match_gitdir(
  	int *matches,
  	const git_repository *repo,
  	const char *cfg_file,
  	const char *value)
  {
  	return do_match_gitdir(matches, repo, cfg_file, value, false);
  }
  
  static int conditional_match_gitdir_i(
  	int *matches,
  	const git_repository *repo,
  	const char *cfg_file,
  	const char *value)
  {
  	return do_match_gitdir(matches, repo, cfg_file, value, true);
  }
  
  static int conditional_match_onbranch(
  	int *matches,
  	const git_repository *repo,
  	const char *cfg_file,
  	const char *condition)
  {
  	git_str reference = GIT_STR_INIT, buf = GIT_STR_INIT;
  	int error;
  
  	GIT_UNUSED(cfg_file);
  
  	/*
  	 * NOTE: you cannot use `git_repository_head` here. Looking up the
  	 * HEAD reference will create the ODB, which causes us to read the
  	 * repo's config for keys like core.precomposeUnicode. As we're
  	 * just parsing the config right now, though, this would result in
  	 * an endless recursion.
  	 */
  
  	if ((error = git_str_joinpath(&buf, git_repository_path(repo), GIT_HEAD_FILE)) < 0 ||
  	    (error = git_futils_readbuffer(&reference, buf.ptr)) < 0)
  		goto out;
  	git_str_rtrim(&reference);
  
  	if (git__strncmp(reference.ptr, GIT_SYMREF, strlen(GIT_SYMREF)))
  		goto out;
  	git_str_consume(&reference, reference.ptr + strlen(GIT_SYMREF));
  
  	if (git__strncmp(reference.ptr, GIT_REFS_HEADS_DIR, strlen(GIT_REFS_HEADS_DIR)))
  		goto out;
  	git_str_consume(&reference, reference.ptr + strlen(GIT_REFS_HEADS_DIR));
  
  	/*
  	 * If the condition ends with a '/', then we should treat it as if
  	 * it had '**' appended.
  	 */
  	if ((error = git_str_sets(&buf, condition)) < 0)
  		goto out;
  	if (git_fs_path_is_dirsep(condition[strlen(condition) - 1]) &&
  	    (error = git_str_puts(&buf, "**")) < 0)
  		goto out;
  
  	*matches = wildmatch(buf.ptr, reference.ptr, WM_PATHNAME) == WM_MATCH;
  out:
  	git_str_dispose(&reference);
  	git_str_dispose(&buf);
  
  	return error;
  
  }
  
  static const struct {
  	const char *prefix;
  	int (*matches)(int *matches, const git_repository *repo, const char *cfg, const char *value);
  } conditions[] = {
  	{ "gitdir:", conditional_match_gitdir },
  	{ "gitdir/i:", conditional_match_gitdir_i },
  	{ "onbranch:", conditional_match_onbranch }
  };
  
  static int parse_conditional_include(config_file_parse_data *parse_data, const char *section, const char *file)
  {
  	char *condition;
  	size_t section_len, i;
  	int error = 0, matches;
  
  	if (!parse_data->repo || !file)
  		return 0;
  
  	section_len = strlen(section);
  
  	/*
  	 * We checked that the string starts with `includeIf.` and ends
  	 * in `.path` to get here.  Make sure it consists of more.
  	 */
  	if (section_len < CONST_STRLEN("includeIf.") + CONST_STRLEN(".path"))
  		return 0;
  
  	condition = git__substrdup(section + CONST_STRLEN("includeIf."),
  		section_len - CONST_STRLEN("includeIf.") - CONST_STRLEN(".path"));
  
  	GIT_ERROR_CHECK_ALLOC(condition);
  
  	for (i = 0; i < ARRAY_SIZE(conditions); i++) {
  		if (git__prefixcmp(condition, conditions[i].prefix))
  			continue;
  
  		if ((error = conditions[i].matches(&matches,
  						   parse_data->repo,
  						   parse_data->file->path,
  						   condition + strlen(conditions[i].prefix))) < 0)
  			break;
  
  		if (matches)
  			error = parse_include(parse_data, file);
  
  		break;
  	}
  
  	git__free(condition);
  	return error;
  }
  
  static int read_on_variable(
  	git_config_parser *reader,
  	const char *current_section,
  	const char *var_name,
  	const char *var_value,
  	const char *line,
  	size_t line_len,
  	void *data)
  {
  	config_file_parse_data *parse_data = (config_file_parse_data *)data;
  	git_str buf = GIT_STR_INIT;
  	git_config_entry *entry;
  	const char *c;
  	int result = 0;
  
  	GIT_UNUSED(reader);
  	GIT_UNUSED(line);
  	GIT_UNUSED(line_len);
  
  	if (current_section) {
  		/* TODO: Once warnings lang, we should likely warn
  		 * here. Git appears to warn in most cases if it sees
  		 * un-namespaced config options.
  		 */
  		git_str_puts(&buf, current_section);
  		git_str_putc(&buf, '.');
  	}
  
  	for (c = var_name; *c; c++)
  		git_str_putc(&buf, git__tolower(*c));
  
  	if (git_str_oom(&buf))
  		return -1;
  
  	entry = git__calloc(1, sizeof(git_config_entry));
  	GIT_ERROR_CHECK_ALLOC(entry);
  	entry->name = git_str_detach(&buf);
  	entry->value = var_value ? git__strdup(var_value) : NULL;
  	entry->level = parse_data->level;
  	entry->include_depth = parse_data->depth;
  
  	if ((result = git_config_entries_append(parse_data->entries, entry)) < 0)
  		return result;
  
  	result = 0;
  
  	/* Add or append the new config option */
  	if (!git__strcmp(entry->name, "include.path"))
  		result = parse_include(parse_data, entry->value);
  	else if (!git__prefixcmp(entry->name, "includeif.") &&
  	         !git__suffixcmp(entry->name, ".path"))
  		result = parse_conditional_include(parse_data, entry->name, entry->value);
  
  	return result;
  }
  
  static int config_file_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)
  {
  	config_file_parse_data parse_data;
  	git_config_parser reader;
  	int error;
  
  	if (depth >= MAX_INCLUDE_DEPTH) {
  		git_error_set(GIT_ERROR_CONFIG, "maximum config include depth reached");
  		return -1;
  	}
  
  	/* Initialize the reading position */
  	reader.path = file->path;
  	git_parse_ctx_init(&reader.ctx, buf, buflen);
  
  	/* If the file is empty, there's nothing for us to do */
  	if (!reader.ctx.content || *reader.ctx.content == '\0') {
  		error = 0;
  		goto out;
  	}
  
  	parse_data.repo = repo;
  	parse_data.file = file;
  	parse_data.entries = entries;
  	parse_data.level = level;
  	parse_data.depth = depth;
  
  	error = git_config_parse(&reader, NULL, read_on_variable, NULL, NULL, &parse_data);
  
  out:
  	return error;
  }
  
  static int config_file_read(
  	git_config_entries *entries,
  	const git_repository *repo,
  	config_file *file,
  	git_config_level_t level,
  	int depth)
  {
  	git_str contents = GIT_STR_INIT;
  	struct stat st;
  	int error;
  
  	if (p_stat(file->path, &st) < 0) {
  		error = git_fs_path_set_error(errno, file->path, "stat");
  		goto out;
  	}
  
  	if ((error = git_futils_readbuffer(&contents, file->path)) < 0)
  		goto out;
  
  	git_futils_filestamp_set_from_stat(&file->stamp, &st);
  	if ((error = git_hash_buf(file->checksum, contents.ptr, contents.size, GIT_HASH_ALGORITHM_SHA1)) < 0)
  		goto out;
  
  	if ((error = config_file_read_buffer(entries, repo, file, level, depth,
  					     contents.ptr, contents.size)) < 0)
  		goto out;
  
  out:
  	git_str_dispose(&contents);
  	return error;
  }
  
  static int write_section(git_str *fbuf, const char *key)
  {
  	int result;
  	const char *dot;
  	git_str buf = GIT_STR_INIT;
  
  	/* All of this just for [section "subsection"] */
  	dot = strchr(key, '.');
  	git_str_putc(&buf, '[');
  	if (dot == NULL) {
  		git_str_puts(&buf, key);
  	} else {
  		char *escaped;
  		git_str_put(&buf, key, dot - key);
  		escaped = escape_value(dot + 1);
  		GIT_ERROR_CHECK_ALLOC(escaped);
  		git_str_printf(&buf, " \"%s\"", escaped);
  		git__free(escaped);
  	}
  	git_str_puts(&buf, "]\n");
  
  	if (git_str_oom(&buf))
  		return -1;
  
  	result = git_str_put(fbuf, git_str_cstr(&buf), buf.size);
  	git_str_dispose(&buf);
  
  	return result;
  }
  
  static const char *quotes_for_value(const char *value)
  {
  	const char *ptr;
  
  	if (value[0] == ' ' || value[0] == '\0')
  		return "\"";
  
  	for (ptr = value; *ptr; ++ptr) {
  		if (*ptr == ';' || *ptr == '#')
  			return "\"";
  	}
  
  	if (ptr[-1] == ' ')
  		return "\"";
  
  	return "";
  }
  
  struct write_data {
  	git_str *buf;
  	git_str buffered_comment;
  	unsigned int in_section : 1,
  		preg_replaced : 1;
  	const char *orig_section;
  	const char *section;
  	const char *orig_name;
  	const char *name;
  	const git_regexp *preg;
  	const char *value;
  };
  
  static int write_line_to(git_str *buf, const char *line, size_t line_len)
  {
  	int result = git_str_put(buf, line, line_len);
  
  	if (!result && line_len && line[line_len-1] != '\n')
  		result = git_str_printf(buf, "\n");
  
  	return result;
  }
  
  static int write_line(struct write_data *write_data, const char *line, size_t line_len)
  {
  	return write_line_to(write_data->buf, line, line_len);
  }
  
  static int write_value(struct write_data *write_data)
  {
  	const char *q;
  	int result;
  
  	q = quotes_for_value(write_data->value);
  	result = git_str_printf(write_data->buf,
  		"\t%s = %s%s%s\n", write_data->orig_name, q, write_data->value, q);
  
  	/* If we are updating a single name/value, we're done.  Setting `value`
  	 * to `NULL` will prevent us from trying to write it again later (in
  	 * `write_on_section`) if we see the same section repeated.
  	 */
  	if (!write_data->preg)
  		write_data->value = NULL;
  
  	return result;
  }
  
  static int write_on_section(
  	git_config_parser *reader,
  	const char *current_section,
  	const char *line,
  	size_t line_len,
  	void *data)
  {
  	struct write_data *write_data = (struct write_data *)data;
  	int result = 0;
  
  	GIT_UNUSED(reader);
  
  	/* If we were previously in the correct section (but aren't anymore)
  	 * and haven't written our value (for a simple name/value set, not
  	 * a multivar), then append it to the end of the section before writing
  	 * the new one.
  	 */
  	if (write_data->in_section && !write_data->preg && write_data->value)
  		result = write_value(write_data);
  
  	write_data->in_section = strcmp(current_section, write_data->section) == 0;
  
  	/*
  	 * If there were comments just before this section, dump them as well.
  	 */
  	if (!result) {
  		result = git_str_put(write_data->buf, write_data->buffered_comment.ptr, write_data->buffered_comment.size);
  		git_str_clear(&write_data->buffered_comment);
  	}
  
  	if (!result)
  		result = write_line(write_data, line, line_len);
  
  	return result;
  }
  
  static int write_on_variable(
  	git_config_parser *reader,
  	const char *current_section,
  	const char *var_name,
  	const char *var_value,
  	const char *line,
  	size_t line_len,
  	void *data)
  {
  	struct write_data *write_data = (struct write_data *)data;
  	bool has_matched = false;
  	int error;
  
  	GIT_UNUSED(reader);
  	GIT_UNUSED(current_section);
  
  	/*
  	 * If there were comments just before this variable, let's dump them as well.
  	 */
  	if ((error = git_str_put(write_data->buf, write_data->buffered_comment.ptr, write_data->buffered_comment.size)) < 0)
  		return error;
  
  	git_str_clear(&write_data->buffered_comment);
  
  	/* See if we are to update this name/value pair; first examine name */
  	if (write_data->in_section &&
  		strcasecmp(write_data->name, var_name) == 0)
  		has_matched = true;
  
  	/* If we have a regex to match the value, see if it matches */
  	if (has_matched && write_data->preg != NULL)
  		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.
  	 */
  	if (!has_matched)
  		return write_line(write_data, line, line_len);
  
  	write_data->preg_replaced = 1;
  
  	/* If value is NULL, we are deleting this value; write nothing. */
  	if (!write_data->value)
  		return 0;
  
  	return write_value(write_data);
  }
  
  static int write_on_comment(git_config_parser *reader, const char *line, size_t line_len, void *data)
  {
  	struct write_data *write_data;
  
  	GIT_UNUSED(reader);
  
  	write_data = (struct write_data *)data;
  	return write_line_to(&write_data->buffered_comment, line, line_len);
  }
  
  static int write_on_eof(
  	git_config_parser *reader, const char *current_section, void *data)
  {
  	struct write_data *write_data = (struct write_data *)data;
  	int result = 0;
  
  	GIT_UNUSED(reader);
  
  	/*
  	 * If we've buffered comments when reaching EOF, make sure to dump them.
  	 */
  	if ((result = git_str_put(write_data->buf, write_data->buffered_comment.ptr, write_data->buffered_comment.size)) < 0)
  		return result;
  
  	/* If we are at the EOF and have not written our value (again, for a
  	 * simple name/value set, not a multivar) then we have never seen the
  	 * section in question and should create a new section and write the
  	 * value.
  	 */
  	if ((!write_data->preg || !write_data->preg_replaced) && write_data->value) {
  		/* write the section header unless we're already in it */
  		if (!current_section || strcmp(current_section, write_data->section))
  			result = write_section(write_data->buf, write_data->orig_section);
  
  		if (!result)
  			result = write_value(write_data);
  	}
  
  	return result;
  }
  
  /*
   * This is pretty much the parsing, except we write out anything we don't have
   */
  static int config_file_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_str buf = GIT_STR_INIT, contents = GIT_STR_INIT;
  	git_config_parser parser = GIT_CONFIG_PARSER_INIT;
  	git_filebuf file = GIT_FILEBUF_INIT;
  	struct write_data write_data;
  	int error;
  
  	memset(&write_data, 0, sizeof(write_data));
  
  	if (cfg->locked) {
  		error = git_str_puts(&contents, git_str_cstr(&cfg->locked_content) == NULL ? "" : git_str_cstr(&cfg->locked_content));
  	} else {
  		if ((error = git_filebuf_open(&file, cfg->file.path, GIT_FILEBUF_HASH_CONTENTS,
  					      GIT_CONFIG_FILE_MODE)) < 0)
  			goto done;
  
  		/* We need to read in our own config file */
  		error = git_futils_readbuffer(&contents, cfg->file.path);
  	}
  	if (error < 0 && error != GIT_ENOTFOUND)
  		goto done;
  
  	if ((git_config_parser_init(&parser, cfg->file.path, contents.ptr, contents.size)) < 0)
  		goto done;
  
  	ldot = strrchr(key, '.');
  	name = ldot + 1;
  	section = git__strndup(key, ldot - key);
  	GIT_ERROR_CHECK_ALLOC(section);
  
  	ldot = strrchr(orig_key, '.');
  	orig_name = ldot + 1;
  	orig_section = git__strndup(orig_key, ldot - orig_key);
  	GIT_ERROR_CHECK_ALLOC(orig_section);
  
  	write_data.buf = &buf;
  	write_data.orig_section = orig_section;
  	write_data.section = section;
  	write_data.orig_name = orig_name;
  	write_data.name = name;
  	write_data.preg = preg;
  	write_data.value = value;
  
  	if ((error = git_config_parse(&parser, write_on_section, write_on_variable,
  				      write_on_comment, write_on_eof, &write_data)) < 0)
  		goto done;
  
  	if (cfg->locked) {
  		size_t len = buf.asize;
  		/* Update our copy with the modified contents */
  		git_str_dispose(&cfg->locked_content);
  		git_str_attach(&cfg->locked_content, git_str_detach(&buf), len);
  	} else {
  		git_filebuf_write(&file, git_str_cstr(&buf), git_str_len(&buf));
  
  		if ((error = git_filebuf_commit(&file)) < 0)
  			goto done;
  
  		if ((error = config_file_refresh_from_buffer(&cfg->parent, buf.ptr, buf.size)) < 0)
  			goto done;
  	}
  
  done:
  	git__free(section);
  	git__free(orig_section);
  	git_str_dispose(&write_data.buffered_comment);
  	git_str_dispose(&buf);
  	git_str_dispose(&contents);
  	git_filebuf_cleanup(&file);
  	git_config_parser_dispose(&parser);
  
  	return error;
  }
  

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