Curl_add_custom_headers: support headers with no data

A custom HTTP header ending in a semicolon instead of a colon
will be treated as a header to be added without any data
portion.

RELEASE-NOTES

@@ -9,7 +9,7 @@ Curl and libcurl 7.22.1
 
 This release includes the following changes:
 
- o 
+ o Empty headers can be sent in HTTP requests by terminating with a semicolon
 
 This release includes the following bugfixes:
 
@@ -22,6 +22,6 @@ This release includes the following known bugs:
 This release would not have looked like this without help, code, reports and
 advice from friends like these:
 
- 
+ Yukihiro Kawada 
 
         Thanks! (and sorry if I forgot to mention someone)

docs/curl.1

@@ -592,7 +592,9 @@ header will be used instead of the internal one. This allows you to make even
 trickier stuff than curl would normally do. You should not replace internally
 set headers without knowing perfectly well what you're doing. Remove an
 internal header by giving a replacement without content on the right side of
-the colon, as in: -H \&"Host:".
+the colon, as in: -H \&"Host:". If you send the custom header with no-value then
+its header must be terminated with a semicolon, such as \-H "X-Custom-Header;"
+to send "X-Custom-Header:".
 
 curl will make sure that each header you add/replace is sent with the proper
 end-of-line marker, you should thus \fBnot\fP add that as a part of the header

lib/http.c

@@ -1559,6 +1559,31 @@ CURLcode Curl_add_custom_headers(struct connectdata *conn,
         }
       }
     }
+    else {
+      ptr = strchr(headers->data, ';');
+      if(ptr) {
+
+        ptr++; /* pass the semicolon */
+        while(*ptr && ISSPACE(*ptr))
+          ptr++;
+
+        if(*ptr) {
+          /* this may be used for something else in the future */
+        }
+        else {
+          if(*(--ptr) == ';') {
+            CURLcode result;
+
+            /* send no-value custom header if terminated by semicolon */
+            *ptr = ':';
+            result = Curl_add_bufferf(req_buffer, "%s\r\n",
+                                             headers->data);
+            if(result)
+              return result;
+          }
+        }
+      }
+    }
     headers = headers->next;
   }
   return CURLE_OK;

tests/data/test4

@@ -30,7 +30,7 @@ http
 Replaced internal and added custom HTTP headers
  </name>
  <command>
- -H "extra-header: here" -H "Accept: replaced" http://%HOSTIP:%HTTPPORT/4
+ -H "extra-header: here" -H "Accept: replaced" -H "X-Custom-Header;" -H "X-Test: foo; " -H "X-Test:" -H "X-Test2: foo;" -H "X-Test3:  " -H "X-Test4;  " -H "X-Test5;ignored" http://%HOSTIP:%HTTPPORT/4
 </command>
 </client>
 
@@ -45,6 +45,9 @@ GET /4 HTTP/1.1
 Host: %HOSTIP:%HTTPPORT
 extra-header: here
 Accept: replaced
+X-Custom-Header:
+X-Test: foo; 
+X-Test2: foo;
 
 </protocol>
 </verify>