Merge branch 'js/c-merge-recursive'

* js/c-merge-recursive: (21 commits)
  discard_cache(): discard index, even if no file was mmap()ed
  merge-recur: do not die unnecessarily
  merge-recur: try to merge older merge bases first
  merge-recur: if there is no common ancestor, fake empty one
  merge-recur: do not setenv("GIT_INDEX_FILE")
  merge-recur: do not call git-write-tree
  merge-recursive: fix rename handling
  .gitignore: git-merge-recur is a built file.
  merge-recur: virtual commits shall never be parsed
  merge-recur: use the unpack_trees() interface instead of exec()ing read-tree
  merge-recur: fix thinko in unique_path()
  Makefile: git-merge-recur depends on xdiff libraries.
  merge-recur: Explain why sha_eq() and struct stage_data cannot go
  merge-recur: Cleanup last mixedCase variables...
  merge-recur: Fix compiler warning with -pedantic
  merge-recur: Remove dead code
  merge-recur: Get rid of debug code
  merge-recur: Convert variable names to lower_case
  Cumulative update of merge-recursive in C
  recur vs recursive: help testing without touching too many stuff.
  ...

This is an evil merge that removes TEST script from the toplevel.

read-cache.c

@@ -842,6 +842,23 @@ unmap:
 	die("index file corrupt");
 }
 
+int discard_cache()
+{
+	int ret;
+
+	active_nr = active_cache_changed = 0;
+	index_file_timestamp = 0;
+	cache_tree_free(&active_cache_tree);
+	if (cache_mmap == NULL)
+		return 0;
+	ret = munmap(cache_mmap, cache_mmap_size);
+	cache_mmap = NULL;
+	cache_mmap_size = 0;
+
+	/* no need to throw away allocated active_cache */
+	return ret;
+}
+
 #define WRITE_BUFFER_SIZE 8192
 static unsigned char write_buffer[WRITE_BUFFER_SIZE];
 static unsigned long write_buffer_len;