Merge branch 'jl/submodule-mv'

"git mv A B" when moving a submodule A does "the right thing",
inclusing relocating its working tree and adjusting the paths in
the .gitmodules file.

* jl/submodule-mv: (53 commits)
  rm: delete .gitmodules entry of submodules removed from the work tree
  mv: update the path entry in .gitmodules for moved submodules
  submodule.c: add .gitmodules staging helper functions
  mv: move submodules using a gitfile
  mv: move submodules together with their work trees
  rm: do not set a variable twice without intermediate reading.
  t6131 - skip tests if on case-insensitive file system
  parse_pathspec: accept :(icase)path syntax
  pathspec: support :(glob) syntax
  pathspec: make --literal-pathspecs disable pathspec magic
  pathspec: support :(literal) syntax for noglob pathspec
  kill limit_pathspec_to_literal() as it's only used by parse_pathspec()
  parse_pathspec: preserve prefix length via PATHSPEC_PREFIX_ORIGIN
  parse_pathspec: make sure the prefix part is wildcard-free
  rename field "raw" to "_raw" in struct pathspec
  tree-diff: remove the use of pathspec's raw[] in follow-rename codepath
  remove match_pathspec() in favor of match_pathspec_depth()
  remove init_pathspec() in favor of parse_pathspec()
  remove diff_tree_{setup,release}_paths
  convert common_prefix() to use struct pathspec
  ...

tree.c

@@ -47,7 +47,7 @@ static int read_one_entry_quick(const unsigned char *sha1, const char *base, int
 }
 
 static int read_tree_1(struct tree *tree, struct strbuf *base,
-		       int stage, struct pathspec *pathspec,
+		       int stage, const struct pathspec *pathspec,
 		       read_tree_fn_t fn, void *context)
 {
 	struct tree_desc desc;
@@ -116,7 +116,7 @@ static int read_tree_1(struct tree *tree, struct strbuf *base,
 
 int read_tree_recursive(struct tree *tree,
 			const char *base, int baselen,
-			int stage, struct pathspec *pathspec,
+			int stage, const struct pathspec *pathspec,
 			read_tree_fn_t fn, void *context)
 {
 	struct strbuf sb = STRBUF_INIT;