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

The value of "uname -s" is by default sent over the wire as a new
capability, with an opt-out for privacy-concious folks.

* ua/os-version-capability:
  agent: advertise OS name via agent capability
  t5701: add setup test to remove side-effect dependency
  version: extend get_uname_info() to hide system details
  version: refactor get_uname_info()
  version: refactor redact_non_printables()
  version: replace manual ASCII checks with isprint() for clarity

Author: gitster

Documentation/config/transfer.adoc

@@ -125,3 +125,11 @@ transfer.bundleURI::
 transfer.advertiseObjectInfo::
 	When `true`, the `object-info` capability is advertised by
 	servers. Defaults to false.
+
+transfer.advertiseOSInfo::
+	When `true`, both the client and server independently append their
+	operating system name (os) to the `agent` capability value. The `agent`
+	capability will now be in form of "package/version os" (e.g.,
+	"git/1.8.3.1 Linux"). When `false`, the `agent` capability will be
+	in the form of "package/version" e.g "git/1.8.3.1". The server's
+	configuration is independent of the client's. Defaults to `true`.

Documentation/gitprotocol-v2.adoc

@@ -184,11 +184,16 @@ form `agent=X`) to notify the client that the server is running version
 the `agent` capability with a value `Y` (in the form `agent=Y`) in its
 request to the server (but it MUST NOT do so if the server did not
 advertise the agent 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 of the form "package/version" (e.g.,
-"git/1.8.3.1"). The agent strings are purely informative for statistics
-and debugging purposes, and MUST NOT be used to programmatically assume
-the presence or absence of particular features.
+printable ASCII characters (i.e., the byte range 32 < x < 127), and are
+typically of the form "package/version os" (e.g., "git/1.8.3.1 Linux")
+where `os` is the operating system name (e.g., "Linux"). `X` and `Y` can
+be configured using the GIT_USER_AGENT environment variable and it takes
+priority. If `transfer.advertiseOSInfo` is `false` on the server, the server
+omits the `os` from X. If it is `false` on the client, the client omits the
+`os` from `Y`. The `os` is retrieved using the 'sysname' field of the `uname(2)`
+system call or its equivalent. The agent 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);

t/t5555-http-smart-common.sh

@@ -123,9 +123,17 @@ test_expect_success 'git receive-pack --advertise-refs: v1' '
 '
 
 test_expect_success 'git upload-pack --advertise-refs: v2' '
+	printf "agent=FAKE" >agent_capability &&
+	if test_have_prereq WINDOWS
+	then
+		printf "\n" >>agent_capability &&
+		git config transfer.advertiseOSInfo false
+	else
+		printf " %s\n" $(uname -s | test_redact_non_printables) >>agent_capability
+	fi &&
 	cat >expect <<-EOF &&
 	version 2
-	agent=FAKE
+	$(cat agent_capability)
 	ls-refs=unborn
 	fetch=shallow wait-for-done
 	server-option

t/t5701-git-serve.sh

@@ -7,22 +7,35 @@ export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
 
 . ./test-lib.sh
 
-test_expect_success 'test capability advertisement' '
+test_expect_success 'setup to generate files with expected content' '
+	printf "agent=git/%s" "$(git version | cut -d" " -f3)" >agent_capability &&
+
 	test_oid_cache <<-EOF &&
 	wrong_algo sha1:sha256
 	wrong_algo sha256:sha1
 	EOF
+
+	if test_have_prereq WINDOWS
+	then
+		printf "\n" >>agent_capability &&
+		git config transfer.advertiseOSInfo false
+	else
+		printf " %s\n" $(uname -s | test_redact_non_printables) >>agent_capability
+	fi &&
 	cat >expect.base <<-EOF &&
 	version 2
-	agent=git/$(git version | cut -d" " -f3)
+	$(cat agent_capability)
 	ls-refs=unborn
 	fetch=shallow wait-for-done
 	server-option
 	object-format=$(test_oid algo)
 	EOF
-	cat >expect.trailer <<-EOF &&
+	cat >expect.trailer <<-EOF
 	0000
 	EOF
+'
+
+test_expect_success 'test capability advertisement' '
 	cat expect.base expect.trailer >expect &&
 
 	GIT_TEST_SIDEBAND_ALL=0 test-tool serve-v2 \

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
+# correspond to decimal intervals 1-32 and 127-255
+test_redact_non_printables () {
+    tr -d "\n\r" | tr "[\001-\040][\177-\377]" "."
+}

version.c

@@ -1,3 +1,5 @@
+#define USE_THE_REPOSITORY_VARIABLE
+
 #include "git-compat-util.h"
 #include "version.h"
 #include "strbuf.h"
@@ -9,9 +11,16 @@
 # include GIT_VERSION_H
 #endif
 
+#include "gettext.h"
+#include "config.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.
+ */
 void redact_non_printables(struct strbuf *buf)
 {
 	strbuf_trim(buf);
@@ -43,8 +52,63 @@ const char *git_user_agent_sanitized(void)
 
 		strbuf_addstr(&buf, git_user_agent());
 		redact_non_printables(&buf);
+		/* Add os name if the transfer.advertiseosinfo config is true */
+		if (advertise_os_info()) {
+			/* Add space to space character after git version string */
+			strbuf_addch(&buf, ' ');
+			strbuf_addstr(&buf, os_info_sanitized());
+		}
 		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;
+}
+
+const char *os_info_sanitized(void)
+{
+	static const char *os = NULL;
+
+	if (!os) {
+		struct strbuf buf = STRBUF_INIT;
+
+		get_uname_info(&buf, 0);
+		/* Sanitize the os information immediately */
+		redact_non_printables(&buf);
+		os = strbuf_detach(&buf, NULL);
+	}
+
+	return os;
+}
+
+int advertise_os_info(void)
+{
+	static int transfer_advertise_os_info= -1;
+
+	if (transfer_advertise_os_info == -1) {
+		repo_config_get_bool(the_repository, "transfer.advertiseosinfo", &transfer_advertise_os_info);
+		/* enabled by default */
+		transfer_advertise_os_info = !!transfer_advertise_os_info;
+	}
+	return transfer_advertise_os_info;
+}

version.h

@@ -1,6 +1,8 @@
 #ifndef VERSION_H
 #define VERSION_H
 
+struct repository;
+
 extern const char git_version_string[];
 extern const char git_built_from_commit_string[];
 
@@ -15,4 +17,24 @@ const char *git_user_agent_sanitized(void);
 */
 void redact_non_printables(struct strbuf *buf);
 
+/*
+  Try to get information about the system using uname(2).
+  Return -1 and put an error message into 'buf' in case of uname()
+  error. Return 0 and put uname info into 'buf' otherwise.
+*/
+int get_uname_info(struct strbuf *buf, unsigned int full);
+
+/*
+  Retrieve, sanitize and cache operating system info for subsequent
+  calls. Return a pointer to the sanitized operating system info
+  string.
+*/
+const char *os_info_sanitized(void);
+
+/*
+  Retrieve and cache transfer.advertiseosinfo config value. Return 1
+  if true, 0 if false.
+*/
+int advertise_os_info(void);
+
 #endif /* VERSION_H */