Misc tab refactoring (#1424)

* Move tabs logic into utils

* Re-use buffer returned by tabs::expand

* Add TabCfg to configure tabs

Use the String from this config for the tab replacement. This avoids
creating a new String for each processed line.

* Avoid unicode segmentation for each line just to remove a prefix

In some code paths no prefix is removed, and in almost all other
cases the prefix is just ascii.

This simplifies a lot of calls.

* Set default tab with to 8

Editors like vim, emacs, nano and most terminal emulators set
this value as the default tab display width.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/cli.rs b/src/cli.rs
index eb1f9b85..80c73b90 100644
--- a/src/cli.rs
+++ b/src/cli.rs
@@ -935,7 +935,7 @@ pub struct Opt {
     /// syntax highlighting.
     pub syntax_theme: Option<String>,
 
-    #[arg(long = "tabs", default_value = "4", value_name = "N")]
+    #[arg(long = "tabs", default_value = "8", value_name = "N")]
     /// The number of spaces to replace tab characters with.
     ///
     /// Use --tabs=0 to pass tab characters through directly, but note that in that case delta will