Index: subversion/libsvn_ra_neon/commit.c
===================================================================
--- subversion/libsvn_ra_neon/commit.c	(revision 37906)
+++ subversion/libsvn_ra_neon/commit.c	(working copy)
@@ -1177,6 +1177,7 @@
   resource_baton_t *file = file_baton;
   put_baton_t *baton;
   svn_stream_t *stream;
+  const char *tempfile_name;
 
   baton = apr_pcalloc(file->pool, sizeof(*baton));
   baton->ras = file->cc->ras;
@@ -1195,10 +1196,31 @@
   /* Create a temp file in the system area to hold the contents. Note that
      we need a file since we will be rewinding it. The file will be closed
      and deleted when the pool is cleaned up. */
-  SVN_ERR(svn_io_open_unique_file3(&baton->tmpfile, NULL, NULL,
-                                   svn_io_file_del_on_pool_cleanup,
-                                   file->pool, pool));
 
+  /* Avoid temp file name collisions by requesting unique temp file name
+     based on BASE_CHECKSUM or (for newly added paths) the checksum of
+     FILE->RSRC->LOCAL_PATH. */
+  if (base_checksum)
+    {
+      tempfile_name = base_checksum;
+    }
+  else
+    {
+      svn_checksum_t *checksum;
+      SVN_ERR(svn_checksum(&checksum, svn_checksum_md5,
+                           file->rsrc->local_path,
+                           strlen(file->rsrc->local_path),
+                           pool));
+      tempfile_name = apr_psprintf(pool, "tempfile.%s",
+                                   svn_checksum_to_cstring_display(checksum,
+                                                                   pool));  
+    }
+
+  SVN_ERR(svn_io_open_uniquely_named(&baton->tmpfile, NULL, NULL,
+                                     tempfile_name, ".tmp",
+                                     svn_io_file_del_on_pool_cleanup,
+                                     file->pool, pool));
+
   stream = svn_stream_create(baton, pool);
   svn_stream_set_write(stream, commit_stream_write);
 
Index: subversion/libsvn_ra_serf/commit.c
===================================================================
--- subversion/libsvn_ra_serf/commit.c	(revision 37906)
+++ subversion/libsvn_ra_serf/commit.c	(working copy)
@@ -1743,7 +1743,9 @@
   file_context_t *ctx = file_baton;
   const svn_ra_callbacks2_t *wc_callbacks;
   void *wc_callback_baton;
+  const char *tempfile_name;
 
+
   /* Store the stream in a temporary file; we'll give it to serf when we
    * close this file.
    *
@@ -1755,10 +1757,28 @@
   wc_callbacks = ctx->commit->session->wc_callbacks;
   wc_callback_baton = ctx->commit->session->wc_callback_baton;
 
-  SVN_ERR(svn_io_open_unique_file3(&ctx->svndiff, NULL, NULL,
-                                   svn_io_file_del_on_pool_cleanup,
-                                   ctx->pool, ctx->pool));
+  /* Avoid temp file name collisions by requesting unique temp file name
+     based on BASE_CHECKSUM or (for newly added paths) the checksum of
+     CTX->NAME. */
+  if (base_checksum)
+    {
+      tempfile_name = base_checksum;
+    }
+  else
+    {
+      svn_checksum_t *checksum;
+      SVN_ERR(svn_checksum(&checksum, svn_checksum_md5,
+                           ctx->name, strlen(ctx->name), ctx->pool));
+      tempfile_name = apr_psprintf(ctx->pool, "tempfile.%s",
+                                   svn_checksum_to_cstring_display(checksum,
+                                                                   ctx->pool));  
+    }
 
+  SVN_ERR(svn_io_open_uniquely_named(&ctx->svndiff, NULL, NULL,
+                                     tempfile_name, ".tmp",
+                                     svn_io_file_del_on_pool_cleanup,
+                                     ctx->pool, ctx->pool));
+
   ctx->stream = svn_stream_create(ctx, pool);
   svn_stream_set_write(ctx->stream, svndiff_stream_write);