308 side by side tabs (#459)

* Add #308 bug reproduction

delta --no-gitconfig --diff-highlight --side-by-side < etc/examples/308-side-by-side-tabs.diff

* Expand tabs under diff-highlight and diff-so-fancy

Fixes #308

Author: dandavison

etc/examples/308-side-by-side-tabs.diff

@@ -0,0 +1,12 @@
+diff --git .config/git/config .config/git/config
+index bc4ae2e..b058f99 100644
+--- .config/git/config
++++ .config/git/config
+@@ -26,7 +21,6 @@
+ 	# Show summary of changes to submodules. See also:
+ 	# https://git-scm.com/book/en/v2/Git-Tools-Submodules
+ 	submoduleSummary = true
+-	showStash = true
+
+ [diff]
+ 	tool = vimdiff

src/features/diff_highlight.rs

@@ -7,13 +7,11 @@ pub fn make_feature() -> Vec<(String, OptionValueFunction)> {
 
 pub fn _make_feature(bold: bool) -> Vec<(String, OptionValueFunction)> {
     let mut feature = raw::make_feature();
+    feature = feature
+        .into_iter()
+        .filter(|(s, _)| s != "keep-plus-minus-markers" && s != "tabs")
+        .collect();
     feature.extend(builtin_feature!([
-        (
-            "keep-plus-minus-markers",
-            bool,
-            None,
-            _opt => false
-        ),
         (
             "minus-style",
             String,