core.fsync: add configuration parsing

This change introduces code to parse the core.fsync setting and
configure the fsync_components variable.

core.fsync is configured as a comma-separated list of component names to
sync. Each time a core.fsync variable is encountered in the
configuration heirarchy, we start off with a clean state with the
platform default value. Passing 'none' resets the value to indicate
nothing will be synced. We gather all negative and positive entries from
the comma separated list and then compute the new value by removing all
the negative entries and adding all of the positive entries.

We issue a warning for components that are not recognized so that the
configuration code is compatible with configs from future versions of
Git with more repo components.

Complete documentation for the new setting is included in a later patch
in the series so that it can be reviewed once in final form.

Signed-off-by: Neeraj Singh <neerajsi@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 76 insertions, 0 deletions

diff --git a/config.c b/config.c
index f3ff80b..94a4598 100644
--- a/config.c
+++ b/config.c
@@ -1323,6 +1323,73 @@ static int git_parse_maybe_bool_text(const char *value)
 	return -1;
 }
 
+static const struct fsync_component_name {
+	const char *name;
+	enum fsync_component component_bits;
+} fsync_component_names[] = {
+	{ "loose-object", FSYNC_COMPONENT_LOOSE_OBJECT },
+	{ "pack", FSYNC_COMPONENT_PACK },
+	{ "pack-metadata", FSYNC_COMPONENT_PACK_METADATA },
+	{ "commit-graph", FSYNC_COMPONENT_COMMIT_GRAPH },
+};
+
+static enum fsync_component parse_fsync_components(const char *var, const char *string)
+{
+	enum fsync_component current = FSYNC_COMPONENTS_DEFAULT;
+	enum fsync_component positive = 0, negative = 0;
+
+	while (string) {
+		int i;
+		size_t len;
+		const char *ep;
+		int negated = 0;
+		int found = 0;
+
+		string = string + strspn(string, ", \t\n\r");
+		ep = strchrnul(string, ',');
+		len = ep - string;
+		if (!strcmp(string, "none")) {
+			current = FSYNC_COMPONENT_NONE;
+			goto next_name;
+		}
+
+		if (*string == '-') {
+			negated = 1;
+			string++;
+			len--;
+			if (!len)
+				warning(_("invalid value for variable %s"), var);
+		}
+
+		if (!len)
+			break;
+
+		for (i = 0; i < ARRAY_SIZE(fsync_component_names); ++i) {
+			const struct fsync_component_name *n = &fsync_component_names[i];
+
+			if (strncmp(n->name, string, len))
+				continue;
+
+			found = 1;
+			if (negated)
+				negative |= n->component_bits;
+			else
+				positive |= n->component_bits;
+		}
+
+		if (!found) {
+			char *component = xstrndup(string, len);
+			warning(_("ignoring unknown core.fsync component '%s'"), component);
+			free(component);
+		}
+
+next_name:
+		string = ep;
+	}
+
+	return (current & ~negative) | positive;
+}
+
 int git_parse_maybe_bool(const char *value)
 {
 	int v = git_parse_maybe_bool_text(value);
@@ -1600,6 +1667,13 @@ static int git_default_core_config(const char *var, const char *value, void *cb)
 		return 0;
 	}
 
+	if (!strcmp(var, "core.fsync")) {
+		if (!value)
+			return config_error_nonbool(var);
+		fsync_components = parse_fsync_components(var, value);
+		return 0;
+	}
+
 	if (!strcmp(var, "core.fsyncmethod")) {
 		if (!value)
 			return config_error_nonbool(var);
@@ -1613,6 +1687,8 @@ static int git_default_core_config(const char *var, const char *value, void *cb)
 	}
 
 	if (!strcmp(var, "core.fsyncobjectfiles")) {
+		if (fsync_object_files < 0)
+			warning(_("core.fsyncobjectfiles is deprecated; use core.fsync instead"));
 		fsync_object_files = git_config_bool(var, value);
 		return 0;
 	}