Merge branch 'hv/config-from-blob'

Allow configuration data to be read from in-tree blob objects,
which would help working in a bare repository and submodule
updates.

* hv/config-from-blob:
  do not die when error in config parsing of buf occurs
  teach config --blob option to parse config from database
  config: make parsing stack struct independent from actual data source
  config: drop cf validity check in get_next_char()
  config: factor out config file stack management

5 files changed, 278 insertions, 53 deletions

diff --git a/Documentation/git-config.txt b/Documentation/git-config.txt
index 99dc497b6f..34b0894646 100644
--- a/Documentation/git-config.txt
+++ b/Documentation/git-config.txt
@@ -127,6 +127,13 @@ See also <<FILES>>.
 --file config-file::
 	Use the given config file instead of the one specified by GIT_CONFIG.
 
+--blob blob::
+	Similar to '--file' but use the given blob instead of a file. E.g.
+	you can use 'master:.gitmodules' to read values from the file
+	'.gitmodules' in the master branch. See "SPECIFYING REVISIONS"
+	section in linkgit:gitrevisions[7] for a more complete list of
+	ways to spell blob names.
+
 --remove-section::
 	Remove the given section from the configuration file.
 
diff --git a/builtin/config.c b/builtin/config.c
index 7759671eb8..4010c4320a 100644
--- a/builtin/config.c
+++ b/builtin/config.c
@@ -21,6 +21,7 @@ static char term = '\n';
 
 static int use_global_config, use_system_config, use_local_config;
 static const char *given_config_file;
+static const char *given_config_blob;
 static int actions, types;
 static const char *get_color_slot, *get_colorbool_slot;
 static int end_null;
@@ -53,6 +54,7 @@ static struct option builtin_config_options[] = {
 	OPT_BOOLEAN(0, "system", &use_system_config, N_("use system config file")),
 	OPT_BOOLEAN(0, "local", &use_local_config, N_("use repository config file")),
 	OPT_STRING('f', "file", &given_config_file, N_("file"), N_("use given config file")),
+	OPT_STRING(0, "blob", &given_config_blob, N_("blob-id"), N_("read config from given blob object")),
 	OPT_GROUP(N_("Action")),
 	OPT_BIT(0, "get", &actions, N_("get value: name [value-regex]"), ACTION_GET),
 	OPT_BIT(0, "get-all", &actions, N_("get all values: key [value-regex]"), ACTION_GET_ALL),
@@ -218,7 +220,8 @@ static int get_value(const char *key_, const char *regex_)
 	}
 
 	git_config_with_options(collect_config, &values,
-				given_config_file, respect_includes);
+				given_config_file, given_config_blob,
+				respect_includes);
 
 	ret = !values.nr;
 
@@ -302,7 +305,8 @@ static void get_color(const char *def_color)
 	get_color_found = 0;
 	parsed_color[0] = '\0';
 	git_config_with_options(git_get_color_config, NULL,
-				given_config_file, respect_includes);
+				given_config_file, given_config_blob,
+				respect_includes);
 
 	if (!get_color_found && def_color)
 		color_parse(def_color, "command line", parsed_color);
@@ -331,7 +335,8 @@ static int get_colorbool(int print)
 	get_diff_color_found = -1;
 	get_color_ui_found = -1;
 	git_config_with_options(git_get_colorbool_config, NULL,
-				given_config_file, respect_includes);
+				given_config_file, given_config_blob,
+				respect_includes);
 
 	if (get_colorbool_found < 0) {
 		if (!strcmp(get_colorbool_slot, "color.diff"))
@@ -353,6 +358,12 @@ static int get_colorbool(int print)
 		return get_colorbool_found ? 0 : 1;
 }
 
+static void check_blob_write(void)
+{
+	if (given_config_blob)
+		die("writing config blobs is not supported");
+}
+
 int cmd_config(int argc, const char **argv, const char *prefix)
 {
 	int nongit = !startup_info->have_repository;
@@ -364,7 +375,8 @@ int cmd_config(int argc, const char **argv, const char *prefix)
 			     builtin_config_usage,
 			     PARSE_OPT_STOP_AT_NON_OPTION);
 
-	if (use_global_config + use_system_config + use_local_config + !!given_config_file > 1) {
+	if (use_global_config + use_system_config + use_local_config +
+	    !!given_config_file + !!given_config_blob > 1) {
 		error("only one config file at a time.");
 		usage_with_options(builtin_config_usage, builtin_config_options);
 	}
@@ -443,6 +455,7 @@ int cmd_config(int argc, const char **argv, const char *prefix)
 		check_argc(argc, 0, 0);
 		if (git_config_with_options(show_all_config, NULL,
 					    given_config_file,
+					    given_config_blob,
 					    respect_includes) < 0) {
 			if (given_config_file)
 				die_errno("unable to read config file '%s'",
@@ -455,6 +468,8 @@ int cmd_config(int argc, const char **argv, const char *prefix)
 		check_argc(argc, 0, 0);
 		if (!given_config_file && nongit)
 			die("not in a git directory");
+		if (given_config_blob)
+			die("editing blobs is not supported");
 		git_config(git_default_config, NULL);
 		launch_editor(given_config_file ?
 			      given_config_file : git_path("config"),
@@ -462,6 +477,7 @@ int cmd_config(int argc, const char **argv, const char *prefix)
 	}
 	else if (actions == ACTION_SET) {
 		int ret;
+		check_blob_write();
 		check_argc(argc, 2, 2);
 		value = normalize_value(argv[0], argv[1]);
 		ret = git_config_set_in_file(given_config_file, argv[0], value);
@@ -471,18 +487,21 @@ int cmd_config(int argc, const char **argv, const char *prefix)
 		return ret;
 	}
 	else if (actions == ACTION_SET_ALL) {
+		check_blob_write();
 		check_argc(argc, 2, 3);
 		value = normalize_value(argv[0], argv[1]);
 		return git_config_set_multivar_in_file(given_config_file,
 						       argv[0], value, argv[2], 0);
 	}
 	else if (actions == ACTION_ADD) {
+		check_blob_write();
 		check_argc(argc, 2, 2);
 		value = normalize_value(argv[0], argv[1]);
 		return git_config_set_multivar_in_file(given_config_file,
 						       argv[0], value, "^$", 0);
 	}
 	else if (actions == ACTION_REPLACE_ALL) {
+		check_blob_write();
 		check_argc(argc, 2, 3);
 		value = normalize_value(argv[0], argv[1]);
 		return git_config_set_multivar_in_file(given_config_file,
@@ -505,6 +524,7 @@ int cmd_config(int argc, const char **argv, const char *prefix)
 		return get_value(argv[0], argv[1]);
 	}
 	else if (actions == ACTION_UNSET) {
+		check_blob_write();
 		check_argc(argc, 1, 2);
 		if (argc == 2)
 			return git_config_set_multivar_in_file(given_config_file,
@@ -514,12 +534,14 @@ int cmd_config(int argc, const char **argv, const char *prefix)
 						      argv[0], NULL);
 	}
 	else if (actions == ACTION_UNSET_ALL) {
+		check_blob_write();
 		check_argc(argc, 1, 2);
 		return git_config_set_multivar_in_file(given_config_file,
 						       argv[0], NULL, argv[1], 1);
 	}
 	else if (actions == ACTION_RENAME_SECTION) {
 		int ret;
+		check_blob_write();
 		check_argc(argc, 2, 2);
 		ret = git_config_rename_section_in_file(given_config_file,
 							argv[0], argv[1]);
@@ -530,6 +552,7 @@ int cmd_config(int argc, const char **argv, const char *prefix)
 	}
 	else if (actions == ACTION_REMOVE_SECTION) {
 		int ret;
+		check_blob_write();
 		check_argc(argc, 1, 1);
 		ret = git_config_rename_section_in_file(given_config_file,
 							argv[0], NULL);
diff --git a/cache.h b/cache.h
index 48e147f8ba..3142b6c372 100644
--- a/cache.h
+++ b/cache.h
@@ -1176,11 +1176,15 @@ extern int update_server_info(int);
 typedef int (*config_fn_t)(const char *, const char *, void *);
 extern int git_default_config(const char *, const char *, void *);
 extern int git_config_from_file(config_fn_t fn, const char *, void *);
+extern int git_config_from_buf(config_fn_t fn, const char *name,
+			       const char *buf, size_t len, void *data);
 extern void git_config_push_parameter(const char *text);
 extern int git_config_from_parameters(config_fn_t fn, void *data);
 extern int git_config(config_fn_t fn, void *);
 extern int git_config_with_options(config_fn_t fn, void *,
-				   const char *filename, int respect_includes);
+				   const char *filename,
+				   const char *blob_ref,
+				   int respect_includes);
 extern int git_config_early(config_fn_t fn, void *, const char *repo_config);
 extern int git_parse_ulong(const char *, unsigned long *);
 extern int git_config_int(const char *, const char *);
diff --git a/config.c b/config.c
index d04e8157ab..e13a7b65e7 100644
--- a/config.c
+++ b/config.c
@@ -10,20 +10,69 @@
 #include "strbuf.h"
 #include "quote.h"
 
-typedef struct config_file {
-	struct config_file *prev;
-	FILE *f;
+struct config_source {
+	struct config_source *prev;
+	union {
+		FILE *file;
+		struct config_buf {
+			const char *buf;
+			size_t len;
+			size_t pos;
+		} buf;
+	} u;
 	const char *name;
+	int die_on_error;
 	int linenr;
 	int eof;
 	struct strbuf value;
 	struct strbuf var;
-} config_file;
 
-static config_file *cf;
+	int (*fgetc)(struct config_source *c);
+	int (*ungetc)(int c, struct config_source *conf);
+	long (*ftell)(struct config_source *c);
+};
+
+static struct config_source *cf;
 
 static int zlib_compression_seen;
 
+static int config_file_fgetc(struct config_source *conf)
+{
+	return fgetc(conf->u.file);
+}
+
+static int config_file_ungetc(int c, struct config_source *conf)
+{
+	return ungetc(c, conf->u.file);
+}
+
+static long config_file_ftell(struct config_source *conf)
+{
+	return ftell(conf->u.file);
+}
+
+
+static int config_buf_fgetc(struct config_source *conf)
+{
+	if (conf->u.buf.pos < conf->u.buf.len)
+		return conf->u.buf.buf[conf->u.buf.pos++];
+
+	return EOF;
+}
+
+static int config_buf_ungetc(int c, struct config_source *conf)
+{
+	if (conf->u.buf.pos > 0)
+		return conf->u.buf.buf[--conf->u.buf.pos];
+
+	return EOF;
+}
+
+static long config_buf_ftell(struct config_source *conf)
+{
+	return conf->u.buf.pos;
+}
+
 #define MAX_INCLUDE_DEPTH 10
 static const char include_depth_advice[] =
 "exceeded maximum include depth (%d) while including\n"
@@ -168,27 +217,22 @@ int git_config_from_parameters(config_fn_t fn, void *data)
 
 static int get_next_char(void)
 {
-	int c;
-	FILE *f;
-
-	c = '\n';
-	if (cf && ((f = cf->f) != NULL)) {
-		c = fgetc(f);
-		if (c == '\r') {
-			/* DOS like systems */
-			c = fgetc(f);
-			if (c != '\n') {
-				ungetc(c, f);
-				c = '\r';
-			}
-		}
-		if (c == '\n')
-			cf->linenr++;
-		if (c == EOF) {
-			cf->eof = 1;
-			c = '\n';
+	int c = cf->fgetc(cf);
+
+	if (c == '\r') {
+		/* DOS like systems */
+		c = cf->fgetc(cf);
+		if (c != '\n') {
+			cf->ungetc(c, cf);
+			c = '\r';
 		}
 	}
+	if (c == '\n')
+		cf->linenr++;
+	if (c == EOF) {
+		cf->eof = 1;
+		c = '\n';
+	}
 	return c;
 }
 
@@ -339,7 +383,7 @@ static int get_base_var(struct strbuf *name)
 	}
 }
 
-static int git_parse_file(config_fn_t fn, void *data)
+static int git_parse_source(config_fn_t fn, void *data)
 {
 	int comment = 0;
 	int baselen = 0;
@@ -399,7 +443,10 @@ static int git_parse_file(config_fn_t fn, void *data)
 		if (get_value(fn, data, var) < 0)
 			break;
 	}
-	die("bad config file line %d in %s", cf->linenr, cf->name);
+	if (cf->die_on_error)
+		die("bad config file line %d in %s", cf->linenr, cf->name);
+	else
+		return error("bad config file line %d in %s", cf->linenr, cf->name);
 }
 
 static int parse_unit_factor(const char *end, uintmax_t *val)
@@ -906,6 +953,33 @@ int git_default_config(const char *var, const char *value, void *dummy)
 	return 0;
 }
 
+/*
+ * All source specific fields in the union, die_on_error, name and the callbacks
+ * fgetc, ungetc, ftell of top need to be initialized before calling
+ * this function.
+ */
+static int do_config_from(struct config_source *top, config_fn_t fn, void *data)
+{
+	int ret;
+
+	/* push config-file parsing state stack */
+	top->prev = cf;
+	top->linenr = 1;
+	top->eof = 0;
+	strbuf_init(&top->value, 1024);
+	strbuf_init(&top->var, 1024);
+	cf = top;
+
+	ret = git_parse_source(fn, data);
+
+	/* pop config-file parsing state stack */
+	strbuf_release(&top->value);
+	strbuf_release(&top->var);
+	cf = top->prev;
+
+	return ret;
+}
+
 int git_config_from_file(config_fn_t fn, const char *filename, void *data)
 {
 	int ret;
@@ -913,30 +987,74 @@ int git_config_from_file(config_fn_t fn, const char *filename, void *data)
 
 	ret = -1;
 	if (f) {
-		config_file top;
+		struct config_source top;
 
-		/* push config-file parsing state stack */
-		top.prev = cf;
-		top.f = f;
+		top.u.file = f;
 		top.name = filename;
-		top.linenr = 1;
-		top.eof = 0;
-		strbuf_init(&top.value, 1024);
-		strbuf_init(&top.var, 1024);
-		cf = &top;
-
-		ret = git_parse_file(fn, data);
+		top.die_on_error = 1;
+		top.fgetc = config_file_fgetc;
+		top.ungetc = config_file_ungetc;
+		top.ftell = config_file_ftell;
 
-		/* pop config-file parsing state stack */
-		strbuf_release(&top.value);
-		strbuf_release(&top.var);
-		cf = top.prev;
+		ret = do_config_from(&top, fn, data);
 
 		fclose(f);
 	}
 	return ret;
 }
 
+int git_config_from_buf(config_fn_t fn, const char *name, const char *buf,
+			size_t len, void *data)
+{
+	struct config_source top;
+
+	top.u.buf.buf = buf;
+	top.u.buf.len = len;
+	top.u.buf.pos = 0;
+	top.name = name;
+	top.die_on_error = 0;
+	top.fgetc = config_buf_fgetc;
+	top.ungetc = config_buf_ungetc;
+	top.ftell = config_buf_ftell;
+
+	return do_config_from(&top, fn, data);
+}
+
+static int git_config_from_blob_sha1(config_fn_t fn,
+				     const char *name,
+				     const unsigned char *sha1,
+				     void *data)
+{
+	enum object_type type;
+	char *buf;
+	unsigned long size;
+	int ret;
+
+	buf = read_sha1_file(sha1, &type, &size);
+	if (!buf)
+		return error("unable to load config blob object '%s'", name);
+	if (type != OBJ_BLOB) {
+		free(buf);
+		return error("reference '%s' does not point to a blob", name);
+	}
+
+	ret = git_config_from_buf(fn, name, buf, size, data);
+	free(buf);
+
+	return ret;
+}
+
+static int git_config_from_blob_ref(config_fn_t fn,
+				    const char *name,
+				    void *data)
+{
+	unsigned char sha1[20];
+
+	if (get_sha1(name, sha1) < 0)
+		return error("unable to resolve config blob '%s'", name);
+	return git_config_from_blob_sha1(fn, name, sha1, data);
+}
+
 const char *git_etc_gitconfig(void)
 {
 	static const char *system_wide;
@@ -1002,7 +1120,9 @@ int git_config_early(config_fn_t fn, void *data, const char *repo_config)
 }
 
 int git_config_with_options(config_fn_t fn, void *data,
-			    const char *filename, int respect_includes)
+			    const char *filename,
+			    const char *blob_ref,
+			    int respect_includes)
 {
 	char *repo_config = NULL;
 	int ret;
@@ -1021,6 +1141,8 @@ int git_config_with_options(config_fn_t fn, void *data,
 	 */
 	if (filename)
 		return git_config_from_file(fn, filename, data);
+	else if (blob_ref)
+		return git_config_from_blob_ref(fn, blob_ref, data);
 
 	repo_config = git_pathdup("config");
 	ret = git_config_early(fn, data, repo_config);
@@ -1031,7 +1153,7 @@ int git_config_with_options(config_fn_t fn, void *data,
 
 int git_config(config_fn_t fn, void *data)
 {
-	return git_config_with_options(fn, data, NULL, 1);
+	return git_config_with_options(fn, data, NULL, NULL, 1);
 }
 
 /*
@@ -1063,7 +1185,6 @@ static int store_aux(const char *key, const char *value, void *cb)
 {
 	const char *ep;
 	size_t section_len;
-	FILE *f = cf->f;
 
 	switch (store.state) {
 	case KEY_SEEN:
@@ -1075,7 +1196,7 @@ static int store_aux(const char *key, const char *value, void *cb)
 				return 1;
 			}
 
-			store.offset[store.seen] = ftell(f);
+			store.offset[store.seen] = cf->ftell(cf);
 			store.seen++;
 		}
 		break;
@@ -1102,19 +1223,19 @@ static int store_aux(const char *key, const char *value, void *cb)
 		 * Do not increment matches: this is no match, but we
 		 * just made sure we are in the desired section.
 		 */
-		store.offset[store.seen] = ftell(f);
+		store.offset[store.seen] = cf->ftell(cf);
 		/* fallthru */
 	case SECTION_END_SEEN:
 	case START:
 		if (matches(key, value)) {
-			store.offset[store.seen] = ftell(f);
+			store.offset[store.seen] = cf->ftell(cf);
 			store.state = KEY_SEEN;
 			store.seen++;
 		} else {
 			if (strrchr(key, '.') - key == store.baselen &&
 			      !strncmp(key, store.key, store.baselen)) {
 					store.state = SECTION_SEEN;
-					store.offset[store.seen] = ftell(f);
+					store.offset[store.seen] = cf->ftell(cf);
 			}
 		}
 	}
diff --git a/t/t1307-config-blob.sh b/t/t1307-config-blob.sh
new file mode 100755
index 0000000000..fdc257e66f
--- /dev/null
+++ b/t/t1307-config-blob.sh
@@ -0,0 +1,70 @@
+#!/bin/sh
+
+test_description='support for reading config from a blob'
+. ./test-lib.sh
+
+test_expect_success 'create config blob' '
+	cat >config <<-\EOF &&
+	[some]
+		value = 1
+	EOF
+	git add config &&
+	git commit -m foo
+'
+
+test_expect_success 'list config blob contents' '
+	echo some.value=1 >expect &&
+	git config --blob=HEAD:config --list >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'fetch value from blob' '
+	echo true >expect &&
+	git config --blob=HEAD:config --bool some.value >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'reading non-existing value from blob is an error' '
+	test_must_fail git config --blob=HEAD:config non.existing
+'
+
+test_expect_success 'reading from blob and file is an error' '
+	test_must_fail git config --blob=HEAD:config --system --list
+'
+
+test_expect_success 'reading from missing ref is an error' '
+	test_must_fail git config --blob=HEAD:doesnotexist --list
+'
+
+test_expect_success 'reading from non-blob is an error' '
+	test_must_fail git config --blob=HEAD --list
+'
+
+test_expect_success 'setting a value in a blob is an error' '
+	test_must_fail git config --blob=HEAD:config some.value foo
+'
+
+test_expect_success 'deleting a value in a blob is an error' '
+	test_must_fail git config --blob=HEAD:config --unset some.value
+'
+
+test_expect_success 'editing a blob is an error' '
+	test_must_fail git config --blob=HEAD:config --edit
+'
+
+test_expect_success 'parse errors in blobs are properly attributed' '
+	cat >config <<-\EOF &&
+	[some]
+		value = "
+	EOF
+	git add config &&
+	git commit -m broken &&
+
+	test_must_fail git config --blob=HEAD:config some.value 2>err &&
+
+	# just grep for our token as the exact error message is likely to
+	# change or be internationalized
+	grep "HEAD:config" err
+'
+
+test_done