Merge branch 'ua/os-version-capability' into seen

* ua/os-version-capability:
  version: introduce osversion.command config for os-version output
  connect: advertise OS version
  version: refactor get_uname_info()
  version: refactor redact_non_printables()

Documentation/config/transfer.txt

@@ -125,3 +125,19 @@ transfer.bundleURI::
 transfer.advertiseObjectInfo::
 	When `true`, the `object-info` capability is advertised by
 	servers. Defaults to false.
+
+transfer.advertiseOSVersion::
+	When `true`, the `os-version` capability is advertised by clients and
+	servers. It makes clients and servers send to each other a string
+	representing the operating system name, like "Linux" or "Windows".
+	This string is retrieved from the 'sysname' field of the struct returned
+	by the uname(2) system call. If the `osVersion.command` is set, the
+	output of the command specified will be the string exchanged by the clients
+	and the servers. Defaults to true.
+
+osVersion.command::
+	If this variable is set, the specified command will be run and the output
+	will be used as the value `X` for `os-version` capability (in the form
+	`os-version=X`). `osVersion.command` is only used if `transfer.advertiseOSVersion`
+	is true. Refer to the linkgit:git-config[1] documentation to learn more about
+	`transfer.advertiseOSVersion` config option.

Documentation/gitprotocol-v2.txt

@@ -190,6 +190,27 @@ printable ASCII characters except space (i.e., the byte range 32 < x <
 and debugging purposes, and MUST NOT be used to programmatically assume
 the presence or absence of particular features.
 
+os-version
+~~~~~~~~~~
+
+In the same way as the `agent` capability above, the server can
+advertise the `os-version` capability with a value `X` (in the form
+`os-version=X`) to notify the client that the server is running an
+operating system that can be identified by `X`. The client may
+optionally send its own `os-version` string by including the
+`os-version` capability with a value `Y` (in the form `os-version=Y`)
+in its request to the server (but it MUST NOT do so if the server did
+not advertise the os-version capability). The `X` and `Y` strings may
+contain any printable ASCII characters except space (i.e., the byte
+range 32 < x < 127), and are typically made from the result of
+`uname -s`(OS name e.g Linux).  If the `osVersion.command` is set,
+the `X` and `Y` are made from the ouput of the command specified.
+The os-version capability can be disabled entirely by setting the
+`transfer.advertiseOSVersion` config option to `false`. The `os-version`
+strings are purely informative for statistics and debugging purposes, and
+MUST NOT be used to programmatically assume the presence or absence of
+particular features.
+
 ls-refs
 ~~~~~~~
 

builtin/bugreport.c

@@ -12,10 +12,10 @@
 #include "diagnose.h"
 #include "object-file.h"
 #include "setup.h"
+#include "version.h"
 
 static void get_system_info(struct strbuf *sys_info)
 {
-	struct utsname uname_info;
 	char *shell = NULL;
 
 	/* get git version from native cmd */
@@ -24,16 +24,7 @@ static void get_system_info(struct strbuf *sys_info)
 
 	/* system call for other version info */
 	strbuf_addstr(sys_info, "uname: ");
-	if (uname(&uname_info))
-		strbuf_addf(sys_info, _("uname() failed with error '%s' (%d)\n"),
-			    strerror(errno),
-			    errno);
-	else
-		strbuf_addf(sys_info, "%s %s %s %s\n",
-			    uname_info.sysname,
-			    uname_info.release,
-			    uname_info.version,
-			    uname_info.machine);
+	get_uname_info(sys_info, 1);
 
 	strbuf_addstr(sys_info, _("compiler info: "));
 	get_compiler_info(sys_info);

connect.c

@@ -492,6 +492,9 @@ static void send_capabilities(int fd_out, struct packet_reader *reader)
 	if (server_supports_v2("agent"))
 		packet_write_fmt(fd_out, "agent=%s", git_user_agent_sanitized());
 
+	if (server_supports_v2("os-version") && advertise_os_version(the_repository))
+		packet_write_fmt(fd_out, "os-version=%s", os_version_sanitized());
+
 	if (server_feature_v2("object-format", &hash_name)) {
 		int hash_algo = hash_algo_by_name(hash_name);
 		if (hash_algo == GIT_HASH_UNKNOWN)

serve.c

@@ -29,6 +29,16 @@ static int agent_advertise(struct repository *r UNUSED,
 	return 1;
 }
 
+static int os_version_advertise(struct repository *r,
+			   struct strbuf *value)
+{
+	if (!advertise_os_version(r))
+		return 0;
+	if (value)
+		strbuf_addstr(value, os_version_sanitized());
+	return 1;
+}
+
 static int object_format_advertise(struct repository *r,
 				   struct strbuf *value)
 {
@@ -123,6 +133,10 @@ static struct protocol_capability capabilities[] = {
 		.name = "agent",
 		.advertise = agent_advertise,
 	},
+	{
+		.name = "os-version",
+		.advertise = os_version_advertise,
+	},
 	{
 		.name = "ls-refs",
 		.advertise = ls_refs_advertise,

t/t5555-http-smart-common.sh

@@ -123,9 +123,48 @@ test_expect_success 'git receive-pack --advertise-refs: v1' '
 '
 
 test_expect_success 'git upload-pack --advertise-refs: v2' '
+	printf "agent=FAKE" >agent_and_os_name &&
+	if test_have_prereq WINDOWS
+	then
+		# We do not use test_config here so that any tests below can reuse
+		# the "expect" file from this test
+		git config transfer.advertiseOSVersion false
+	else
+		printf "\nos-version=%s\n" $(uname -s | test_redact_non_printables) >>agent_and_os_name
+	fi &&
+
+	cat >expect <<-EOF &&
+	version 2
+	$(cat agent_and_os_name)
+	ls-refs=unborn
+	fetch=shallow wait-for-done
+	server-option
+	object-format=$(test_oid algo)
+	0000
+	EOF
+
+	GIT_PROTOCOL=version=2 \
+	GIT_USER_AGENT=FAKE \
+	git upload-pack --advertise-refs . >out 2>err &&
+
+	test-tool pkt-line unpack <out >actual &&
+	test_must_be_empty err &&
+	test_cmp actual expect
+'
+
+test_expect_success 'git upload-pack --advertise-refs: v2 with osVersion.command config set' '
+	# test_config is used here as we are not reusing any file output from here
+	test_config osVersion.command "uname -srvm" &&
+	printf "agent=FAKE" >agent_and_long_os_name &&
+
+	if test_have_prereq !WINDOWS
+	then
+		printf "\nos-version=%s\n" $(uname -srvm | test_redact_non_printables) >>agent_and_long_os_name
+	fi &&
+
 	cat >expect <<-EOF &&
 	version 2
-	agent=FAKE
+	$(cat agent_and_long_os_name)
 	ls-refs=unborn
 	fetch=shallow wait-for-done
 	server-option

t/t5701-git-serve.sh

@@ -8,13 +8,23 @@ export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
 . ./test-lib.sh
 
 test_expect_success 'test capability advertisement' '
+	printf "agent=git/$(git version | cut -d" " -f3)" >agent_and_os_name &&
+	if test_have_prereq WINDOWS
+	then
+		# We do not use test_config here so that tests below will be able to reuse
+		# the expect.base and expect.trailer files
+		git config transfer.advertiseOSVersion false
+	else
+		printf "\nos-version=%s\n" $(uname -s | test_redact_non_printables) >>agent_and_os_name
+	fi &&
+
 	test_oid_cache <<-EOF &&
 	wrong_algo sha1:sha256
 	wrong_algo sha256:sha1
 	EOF
 	cat >expect.base <<-EOF &&
 	version 2
-	agent=git/$(git version | cut -d" " -f3)
+	$(cat agent_and_os_name)
 	ls-refs=unborn
 	fetch=shallow wait-for-done
 	server-option
@@ -31,6 +41,39 @@ test_expect_success 'test capability advertisement' '
 	test_cmp expect actual
 '
 
+test_expect_success 'test capability advertisement with osVersion.command config set' '
+	# test_config is used here as we are not reusing any file output from here
+	test_config osVersion.command "uname -srvm" &&
+	printf "agent=git/$(git version | cut -d" " -f3)" >agent_and_long_os_name &&
+
+	if test_have_prereq !WINDOWS
+	then
+		printf "\nos-version=%s\n" $(uname -srvm | test_redact_non_printables) >>agent_and_long_os_name
+	fi &&
+
+	test_oid_cache <<-EOF &&
+	wrong_algo sha1:sha256
+	wrong_algo sha256:sha1
+	EOF
+	cat >expect.base_long <<-EOF &&
+	version 2
+	$(cat agent_and_long_os_name)
+	ls-refs=unborn
+	fetch=shallow wait-for-done
+	server-option
+	object-format=$(test_oid algo)
+	EOF
+	cat >expect.trailer_long <<-EOF &&
+	0000
+	EOF
+	cat expect.base_long expect.trailer_long >expect &&
+
+	GIT_TEST_SIDEBAND_ALL=0 test-tool serve-v2 \
+		--advertise-capabilities >out &&
+	test-tool pkt-line unpack <out >actual &&
+	test_cmp expect actual
+'
+
 test_expect_success 'stateless-rpc flag does not list capabilities' '
 	# Empty request
 	test-tool pkt-line pack >in <<-EOF &&

t/test-lib-functions.sh

@@ -2043,3 +2043,11 @@ test_trailing_hash () {
 		test-tool hexdump |
 		sed "s/ //g"
 }
+
+# Trim and replace each character with ascii code below 32 or above
+# 127 (included) using a dot '.' character.
+# Octal intervals \001-\040 and \177-\377
+# corresponds to decimal intervals 1-32 and 127-255
+test_redact_non_printables () {
+    tr -d "\n" | tr "[\001-\040][\177-\377]" "."
+}

version.c

@@ -1,11 +1,31 @@
+#define USE_THE_REPOSITORY_VARIABLE
+
 #include "git-compat-util.h"
 #include "version.h"
 #include "version-def.h"
 #include "strbuf.h"
+#include "gettext.h"
+#include "config.h"
+#include "run-command.h"
+#include "alias.h"
 
 const char git_version_string[] = GIT_VERSION;
 const char git_built_from_commit_string[] = GIT_BUILT_FROM_COMMIT;
 
+/*
+ * Trim and replace each character with ascii code below 32 or above
+ * 127 (included) using a dot '.' character.
+ * TODO: ensure consecutive non-printable characters are only replaced once
+*/
+static void redact_non_printables(struct strbuf *buf)
+{
+	strbuf_trim(buf);
+	for (size_t i = 0; i < buf->len; i++) {
+		if (buf->buf[i] <= 32 || buf->buf[i] >= 127)
+			buf->buf[i] = '.';
+	}
+}
+
 const char *git_user_agent(void)
 {
 	static const char *agent = NULL;
@@ -27,13 +47,117 @@ const char *git_user_agent_sanitized(void)
 		struct strbuf buf = STRBUF_INIT;
 
 		strbuf_addstr(&buf, git_user_agent());
-		strbuf_trim(&buf);
-		for (size_t i = 0; i < buf.len; i++) {
-			if (buf.buf[i] <= 32 || buf.buf[i] >= 127)
-				buf.buf[i] = '.';
-		}
-		agent = buf.buf;
+		redact_non_printables(&buf);
+		agent = strbuf_detach(&buf, NULL);
 	}
 
 	return agent;
 }
+
+int get_uname_info(struct strbuf *buf, unsigned int full)
+{
+	struct utsname uname_info;
+
+	if (uname(&uname_info)) {
+		strbuf_addf(buf, _("uname() failed with error '%s' (%d)\n"),
+			    strerror(errno),
+			    errno);
+		return -1;
+	}
+
+	if (full)
+		strbuf_addf(buf, "%s %s %s %s\n",
+			    uname_info.sysname,
+			    uname_info.release,
+			    uname_info.version,
+			    uname_info.machine);
+	else
+		strbuf_addf(buf, "%s\n", uname_info.sysname);
+	return 0;
+}
+
+/*
+ * Return -1 if unable to retrieve the osversion.command config or
+ * if the command is malformed; otherwise, return 0 if successful.
+ */
+static int fill_os_version_command(struct child_process *cmd)
+{
+	const char *os_version_command;
+	const char **argv;
+	char *os_version_copy;
+	int n;
+
+	if (git_config_get_string_tmp("osversion.command", &os_version_command))
+		return -1;
+
+	os_version_copy = xstrdup(os_version_command);
+	n = split_cmdline(os_version_copy, &argv);
+
+	if (n < 0) {
+		warning(_("malformed osVersion.command config option: %s"),
+			_(split_cmdline_strerror(n)));
+		free(os_version_copy);
+		return -1;
+	}
+
+	for (int i = 0; i < n; i++)
+		strvec_push(&cmd->args, argv[i]);
+	free(os_version_copy);
+	free(argv);
+
+	return 0;
+}
+
+static int capture_os_version(struct strbuf *buf)
+{
+	struct child_process cmd = CHILD_PROCESS_INIT;
+
+	if (fill_os_version_command(&cmd))
+		return -1;
+	if (capture_command(&cmd, buf, 0))
+		return -1;
+
+	return 0;
+}
+
+const char *os_version(void)
+{
+	static const char *os = NULL;
+
+	if (!os) {
+		struct strbuf buf = STRBUF_INIT;
+
+		if (capture_os_version(&buf))
+			get_uname_info(&buf, 0);
+		os = strbuf_detach(&buf, NULL);
+	}
+
+	return os;
+}
+
+const char *os_version_sanitized(void)
+{
+	static const char *os_sanitized = NULL;
+
+	if (!os_sanitized) {
+		struct strbuf buf = STRBUF_INIT;
+
+		strbuf_addstr(&buf, os_version());
+		redact_non_printables(&buf);
+		os_sanitized = strbuf_detach(&buf, NULL);
+	}
+
+	return os_sanitized;
+}
+
+int advertise_os_version(struct repository *r)
+{
+	static int transfer_advertise_os_version = -1;
+
+	if (transfer_advertise_os_version == -1) {
+		repo_config_get_bool(r, "transfer.advertiseosversion", &transfer_advertise_os_version);
+		/* enabled by default */
+		transfer_advertise_os_version = !!transfer_advertise_os_version;
+	}
+	return transfer_advertise_os_version;
+}