Only print rename information when we're called from git

If the user explicitly runs `$ difft old.js new.js` there's no point
talking about renames.

src/inline.rs

@@ -57,7 +57,9 @@ pub fn print(
                 i + 1,
                 hunks.len(),
                 lang_name,
+                // TODO: Just pass display_options.
                 display_options.use_color,
+                display_options.in_vcs,
                 display_options.background_color
             )
         );

src/main.rs

@@ -422,6 +422,7 @@ fn print_diff_result(display_options: &DisplayOptions, summary: &DiffResult) {
                             1,
                             &lang_name,
                             display_options.use_color,
+                            display_options.in_vcs,
                             display_options.background_color
                         )
                     );
@@ -477,6 +478,7 @@ fn print_diff_result(display_options: &DisplayOptions, summary: &DiffResult) {
                         1,
                         "binary",
                         display_options.use_color,
+                        display_options.in_vcs,
                         display_options.background_color
                     )
                 );
@@ -498,6 +500,7 @@ fn print_diff_result(display_options: &DisplayOptions, summary: &DiffResult) {
                     1,
                     "binary",
                     display_options.use_color,
+                    display_options.in_vcs,
                     display_options.background_color
                 )
             );

src/options.rs

@@ -27,6 +27,7 @@ pub struct DisplayOptions {
     pub print_unchanged: bool,
     pub tab_width: usize,
     pub display_width: usize,
+    pub in_vcs: bool,
     pub syntax_highlight: bool,
 }
 
@@ -232,12 +233,13 @@ pub fn parse_args() -> Mode {
     info!("CLI arguments: {:?}", args);
 
     // TODO: document these different ways of calling difftastic.
-    let (lhs_display_path, rhs_display_path, lhs_path, rhs_path) = match &args[..] {
+    let (lhs_display_path, rhs_display_path, lhs_path, rhs_path, in_vcs) = match &args[..] {
         [lhs_path, rhs_path] => (
             lhs_path.to_owned(),
             rhs_path.to_owned(),
             lhs_path.to_owned(),
             rhs_path.to_owned(),
+            false,
         ),
         [display_path, lhs_tmp_file, _lhs_hash, _lhs_mode, rhs_tmp_file, _rhs_hash, _rhs_mode] => {
             // https://git-scm.com/docs/git#Documentation/git.txt-codeGITEXTERNALDIFFcode
@@ -246,6 +248,7 @@ pub fn parse_args() -> Mode {
                 display_path.to_owned(),
                 lhs_tmp_file.to_owned(),
                 rhs_tmp_file.to_owned(),
+                true,
             )
         }
         [old_name, lhs_tmp_file, _lhs_hash, _lhs_mode, rhs_tmp_file, _rhs_hash, _rhs_mode, new_name, _similarity] =>
@@ -257,6 +260,7 @@ pub fn parse_args() -> Mode {
                 new_name.to_owned(),
                 lhs_tmp_file.to_owned(),
                 rhs_tmp_file.to_owned(),
+                true,
             )
         }
         _ => {
@@ -349,6 +353,7 @@ pub fn parse_args() -> Mode {
         display_mode,
         display_width,
         syntax_highlight,
+        in_vcs,
     };
 
     Mode::Diff {

src/side_by_side.rs

@@ -84,6 +84,7 @@ fn display_single_column(
     src: &str,
     is_lhs: bool,
     use_color: bool,
+    in_vcs: bool,
     background: BackgroundColor,
 ) -> String {
     let column_width = format_line_num(src.lines().count().into()).len();
@@ -96,6 +97,7 @@ fn display_single_column(
         1,
         lang_name,
         use_color,
+        in_vcs,
         background,
     ));
     result.push('\n');
@@ -341,6 +343,7 @@ pub fn print(
                 &rhs_colored_src,
                 false,
                 display_options.use_color,
+                display_options.in_vcs,
                 display_options.background_color
             )
         );
@@ -355,7 +358,9 @@ pub fn print(
                 lang_name,
                 &lhs_colored_src,
                 true,
+                // TODO: pass display_options directly.
                 display_options.use_color,
+                display_options.in_vcs,
                 display_options.background_color
             )
         );
@@ -396,6 +401,7 @@ pub fn print(
                 hunks.len(),
                 lang_name,
                 display_options.use_color,
+                display_options.in_vcs,
                 display_options.background_color
             )
         );
@@ -640,6 +646,7 @@ mod tests {
             "print(123)\n",
             false,
             true,
+            false,
             BackgroundColor::Dark,
         );
         assert!(res.len() > 10);
@@ -720,6 +727,7 @@ mod tests {
             tab_width: 8,
             display_width: 80,
             syntax_highlight: true,
+            in_vcs: true,
         };
 
         // Simple smoke test.

src/style.rs

@@ -344,6 +344,7 @@ pub fn header(
     hunk_total: usize,
     language_name: &str,
     use_color: bool,
+    in_vcs: bool,
     background: BackgroundColor,
 ) -> String {
     let divider = if hunk_total == 1 {
@@ -353,7 +354,7 @@ pub fn header(
     };
 
     let rhs_path_pretty = apply_header_color(rhs_display_path, use_color, background);
-    if hunk_num == 1 && lhs_display_path != rhs_display_path {
+    if hunk_num == 1 && lhs_display_path != rhs_display_path && in_vcs {
         let lhs_path_pretty = apply_header_color(lhs_display_path, use_color, background);
         let renamed = format!("Renamed {} to {}", lhs_path_pretty, rhs_path_pretty,);
         format!(