Rename Stupid::diff_tree_files_status()

This method is a particular invocation of `git diff-tree` meant to
supplement the output of `stg files`. This frees the name `diff_tree_files`
for a more general purpose behavior.

Author: jpgrayson

src/cmd/files.rs

@@ -57,7 +57,7 @@ fn run(matches: &ArgMatches) -> Result<()> {
     let opt_spec = crate::argset::get_one_str(matches, "stgit-revision");
     let commit = parse_stgit_revision(&repo, opt_spec, None)?.peel_to_commit()?;
     let parent = commit.parent(0)?;
-    let mut output = repo.stupid().diff_tree_files(
+    let mut output = repo.stupid().diff_tree_files_status(
         parent.tree_id(),
         commit.tree_id(),
         matches.contains_id("stat"),

src/stupid.rs

@@ -559,7 +559,7 @@ impl<'repo, 'index> StupidContext<'repo, 'index> {
     }
 
     /// Interative diff-tree (for 'stg files').
-    pub(crate) fn diff_tree_files(
+    pub(crate) fn diff_tree_files_status(
         &self,
         tree1: git2::Oid,
         tree2: git2::Oid,