Set HTTP user agent to git/GIT_VERSION

Useful for diagnostics/troubleshooting to know which client versions are
hitting your server.

Signed-off-by: Nick Hengeveld <nickh@reactrix.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>

Makefile

@@ -510,6 +510,9 @@ git$X git.spec \
 exec_cmd.o: exec_cmd.c
 	$(CC) -o $*.o -c $(ALL_CFLAGS) '-DGIT_EXEC_PATH="$(gitexecdir_SQ)"' $<
 
+http.o: http.c
+	$(CC) -o $*.o -c $(ALL_CFLAGS) -DGIT_USER_AGENT='"git/$(GIT_VERSION)"' $<
+
 git-%$X: %.o $(GITLIBS)
 	$(CC) $(ALL_CFLAGS) -o $@ $(ALL_LDFLAGS) $(filter %.o,$^) $(LIBS)
 

http.c

@@ -195,6 +195,8 @@ 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);
+
 	return result;
 }