[PATCH v4] Allow HTTP user agent string to be modified.

["Spencer E. Olson" <olsonse@umich.edu>]

Some firewalls restrict HTTP connections based on the clients user agent.  This
commit provides the user the ability to modify the user agent string via either
a new config option (http.useragent) or by an environment variable
(GIT_USER_AGENT).  Relevant documentation is added to Documentation/config.txt.

Signed-off-by: Spencer E. Olson <olsonse@umich.edu>
---

All,

This includes the changes suggested by Ray Chuan and by Junio Hamano, with one
minor additional change:  This changes the internal -DGIT_USER_AGENT to
-DGIT_HTTP_USER_AGENT.

Since GIT_HTTP_* seems to follow what several of the other HTTP related
environement variables, I agree that using GIT_HTTP_USER_AGENT is better for the
user interface (via env variables) than GIT_USER_AGENT.  I would like to
additionally change the internal token also to GIT_HTTP_USER_AGENT just because
it is clearer for other developers.


 Documentation/config.txt |    9 +++++++++
 Makefile                 |    2 +-
 http.c                   |    9 ++++++++-
 3 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/Documentation/config.txt b/Documentation/config.txt
index f81fb91..7253b71 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -1243,6 +1243,15 @@ http.noEPSV::
 	support EPSV mode. Can be overridden by the 'GIT_CURL_FTP_NO_EPSV'
 	environment variable. Default is false (curl will use EPSV).
 
+http.useragent::
+	The HTTP USER_AGENT string presented to an HTTP server.  The default
+	value represents the version of the client git such as git/1.7.1.
+	This option allows you to override this value to a more common value
+	such as Mozilla/4.0.  This may be necessary, for instance, if
+	connecting through a firewall that restricts HTTP connections to a set
+	of common USER_AGENT strings (but not including those like git/1.7.1).
+	Can be overridden by the 'GIT_HTTP_USER_AGENT' environment variable.
+
 i18n.commitEncoding::
 	Character encoding the commit messages are stored in; git itself
 	does not care per se, but this information is necessary e.g. when
diff --git a/Makefile b/Makefile
index e151516..f84f4a1 100644
--- a/Makefile
+++ b/Makefile
@@ -1873,7 +1873,7 @@ builtin/init-db.s builtin/init-db.o: EXTRA_CPPFLAGS = \
 
 config.s config.o: EXTRA_CPPFLAGS = -DETC_GITCONFIG='"$(ETC_GITCONFIG_SQ)"'
 
-http.s http.o: EXTRA_CPPFLAGS = -DGIT_USER_AGENT='"git/$(GIT_VERSION)"'
+http.s http.o: EXTRA_CPPFLAGS = -DGIT_HTTP_USER_AGENT='"git/$(GIT_VERSION)"'
 
 ifdef NO_EXPAT
 http-walker.s http-walker.o: EXTRA_CPPFLAGS = -DNO_EXPAT
diff --git a/http.c b/http.c
index 1320c50..0a5011f 100644
--- a/http.c
+++ b/http.c
@@ -41,6 +41,7 @@ static long curl_low_speed_time = -1;
 static int curl_ftp_no_epsv;
 static const char *curl_http_proxy;
 static char *user_name, *user_pass;
+static const char *user_agent;
 
 #if LIBCURL_VERSION_NUM >= 0x071700
 /* Use CURLOPT_KEYPASSWD as is */
@@ -196,6 +197,9 @@ static int http_options(const char *var, const char *value, void *cb)
 		return 0;
 	}
 
+	if (!strcmp("http.useragent", var))
+		return git_config_string(&user_agent, var, value);
+
 	/* Fall back on the default ones */
 	return git_default_config(var, value, cb);
 }
@@ -279,7 +283,8 @@ static CURL *get_curl_handle(void)
 	if (getenv("GIT_CURL_VERBOSE"))
 		curl_easy_setopt(result, CURLOPT_VERBOSE, 1);
 
-	curl_easy_setopt(result, CURLOPT_USERAGENT, GIT_USER_AGENT);
+	curl_easy_setopt(result, CURLOPT_USERAGENT,
+		user_agent ? user_agent : GIT_HTTP_USER_AGENT);
 
 	if (curl_ftp_no_epsv)
 		curl_easy_setopt(result, CURLOPT_FTP_USE_EPSV, 0);
@@ -380,6 +385,8 @@ void http_init(struct remote *remote)
 #endif
 	set_from_env(&ssl_cainfo, "GIT_SSL_CAINFO");
 
+	set_from_env(&user_agent, "GIT_HTTP_USER_AGENT");
+
 	low_speed_limit = getenv("GIT_HTTP_LOW_SPEED_LIMIT");
 	if (low_speed_limit != NULL)
 		curl_low_speed_limit = strtol(low_speed_limit, NULL, 10);
-- 
1.7.0.4