[[[
Add support for http_proxy and https_proxy environment variables.

This allows subversion to automatically make use of system-wide proxy
configuration, rather than requiring subversion-specific proxy configuration;
environment variables also make it easier to have network-specific
configuration on machines that use more than one network.  Subversion-specific
configuration (in ~/.subversion/servers) will override the environment.

* subversion/libsvn_ra_serf/serf.c (load_config): Load proxy configuration from
  http_proxy or https_proxy depending on the URI scheme.  Let
  subversion-specific configuration override the environment.
]]]

Index: subversion/libsvn_ra_serf/serf.c
===================================================================
--- subversion/libsvn_ra_serf/serf.c	(revision 1384088)
+++ subversion/libsvn_ra_serf/serf.c	(working copy)
@@ -139,6 +139,7 @@ load_config(svn_ra_serf__session_t *session,
 {
   svn_config_t *config, *config_client;
   const char *server_group;
+  const char *proxy_uri_env = NULL;
   const char *proxy_host = NULL;
   const char *port_str = NULL;
   const char *timeout_str = NULL;
@@ -181,6 +182,25 @@ load_config(svn_ra_serf__session_t *session,
         }
     }
 
+  if (svn_cstring_casecmp(session->session_url.scheme, "http") == 0)
+    proxy_uri_env = getenv("http_proxy");
+  else if (svn_cstring_casecmp(session->session_url.scheme, "https") == 0)
+    proxy_uri_env = getenv("https_proxy");
+  if (proxy_uri_env)
+    {
+      apr_uri_t proxy_uri;
+      if (apr_uri_parse(pool, proxy_uri_env, &proxy_uri))
+        {
+          return svn_error_createf(SVN_ERR_RA_ILLEGAL_URL, NULL,
+                                   _("Invalid proxy URL '%s'"),
+                                   proxy_uri_env);
+        }
+      proxy_host = proxy_uri.hostname;
+      port_str = proxy_uri.port_str;
+      session->proxy_username = proxy_uri.user;
+      session->proxy_password = proxy_uri.password;
+    }
+
   /* Use the default proxy-specific settings if and only if
      "http-proxy-exceptions" is not set to exclude this host. */
   svn_config_get(config, &exceptions, SVN_CONFIG_SECTION_GLOBAL,
@@ -193,17 +213,31 @@ load_config(svn_ra_serf__session_t *session,
     }
   if (! is_exception)
     {
-      /* Load the global proxy server settings, if set. */
-      svn_config_get(config, &proxy_host, SVN_CONFIG_SECTION_GLOBAL,
+      /* Load the global proxy server settings, if set. Override all settings
+       * from the environment if any are set; don't mix settings from config
+       * and environment. */
+      const char *config_proxy_host;
+      const char *config_port_str;
+      const char *config_proxy_username;
+      const char *config_proxy_password;
+      svn_config_get(config, &config_proxy_host, SVN_CONFIG_SECTION_GLOBAL,
                      SVN_CONFIG_OPTION_HTTP_PROXY_HOST, NULL);
-      svn_config_get(config, &port_str, SVN_CONFIG_SECTION_GLOBAL,
+      svn_config_get(config, &config_port_str, SVN_CONFIG_SECTION_GLOBAL,
                      SVN_CONFIG_OPTION_HTTP_PROXY_PORT, NULL);
-      svn_config_get(config, &session->proxy_username,
+      svn_config_get(config, &config_proxy_username,
                      SVN_CONFIG_SECTION_GLOBAL,
                      SVN_CONFIG_OPTION_HTTP_PROXY_USERNAME, NULL);
-      svn_config_get(config, &session->proxy_password,
+      svn_config_get(config, &config_proxy_password,
                      SVN_CONFIG_SECTION_GLOBAL,
                      SVN_CONFIG_OPTION_HTTP_PROXY_PASSWORD, NULL);
+      if (config_proxy_host || config_port_str
+          || config_proxy_username || config_proxy_password)
+        {
+          proxy_host = config_proxy_host;
+          port_str = config_port_str;
+          session->proxy_username = config_proxy_username;
+          session->proxy_password = config_proxy_password;
+        }
     }
 
   /* Load the global ssl settings, if set. */