- Based on Fedor Karpelevitch's formpost path basename patch, file parts in

formposts no longer include the path part. If you _really_ want them, you
  must provide your preferred full file name with CURLFORM_FILENAME.

  Added detection for libgen.h and basename() to configure. My custom
  basename() replacement function for systems without it, might be a bit too
  naive...

  Updated 6 test cases to make them work with the stripped paths.

lib/formdata.c

@@ -113,6 +113,9 @@ Content-Disposition: form-data; name="FILECONTENT"
 #include <stdarg.h>
 #include <time.h>
 #include <sys/stat.h>
+#ifdef HAVE_LIBGEN_H
+#include <libgen.h>
+#endif
 #include "formdata.h"
 #include "strequal.h"
 #include "memory.h"
@@ -903,6 +906,67 @@ void curl_formfree(struct curl_httppost *form)
   } while((form=next)); /* continue */
 }
 
+#ifndef HAVE_BASENAME
+/*
+  (Quote from The Open Group Base Specifications Issue 6 IEEE Std 1003.1, 2004
+  Edition)
+
+  The basename() function shall take the pathname pointed to by path and
+  return a pointer to the final component of the pathname, deleting any
+  trailing '/' characters.
+
+  If the string pointed to by path consists entirely of the '/' character,
+  basename() shall return a pointer to the string "/". If the string pointed
+  to by path is exactly "//", it is implementation-defined whether '/' or "//"
+  is returned.
+
+  If path is a null pointer or points to an empty string, basename() shall
+  return a pointer to the string ".".
+
+  The basename() function may modify the string pointed to by path, and may
+  return a pointer to static storage that may then be overwritten by a
+  subsequent call to basename().
+
+  The basename() function need not be reentrant. A function that is not
+  required to be reentrant is not required to be thread-safe.
+
+*/
+char *basename(char *path)
+{
+  /* Ignore all the details above for now and make a quick and simple
+     implementaion here */
+  char *s1;
+  char *s2;
+
+  s1=strrchr(path, '/');
+  s2=strrchr(path, '\\');
+
+  if(s1 && s2) {
+    path = (s1 > s2? s1 : s2)+1;
+  }
+  else {
+    path = (s1 ? s1 : s2)+1;
+  }
+
+  return path;
+}
+#endif
+
+static char *strippath(char *fullfile)
+{
+  char *filename;
+  char *base;
+  filename = strdup(fullfile); /* duplicate since basename() may ruin the
+                                  buffer it works on */
+  if(!filename)
+    return NULL;
+  base = strdup(basename(filename));
+
+  free(filename); /* free temporary buffer */
+
+  return base; /* returns an allocated string! */
+}
+
 /*
  * Curl_getFormData() converts a linked list of "meta data" into a complete
  * (possibly huge) multipart formdata. The input list is in 'post', while the
@@ -998,22 +1062,33 @@ CURLcode Curl_getFormData(struct FormData **finalform,
 
       if(post->more) {
         /* if multiple-file */
+        char *filebasename=
+          (!file->showfilename)?strippath(file->contents):NULL;
+
         result = AddFormDataf(&form, &size,
                               "\r\n--%s\r\nContent-Disposition: "
                               "attachment; filename=\"%s\"",
                               fileboundary,
                               (file->showfilename?file->showfilename:
-                               file->contents));
+                               filebasename));
+        if (filebasename)
+          free(filebasename);
         if (result)
           break;
       }
       else if((post->flags & HTTPPOST_FILENAME) ||
               (post->flags & HTTPPOST_BUFFER)) {
 
+        char *filebasename=
+          (!post->showfilename)?strippath(post->contents):NULL;
+
         result = AddFormDataf(&form, &size,
                               "; filename=\"%s\"",
                               (post->showfilename?post->showfilename:
-                               post->contents));
+                               filebasename));
+        if (filebasename)
+          free(filebasename);
+
         if (result)
           break;
       }