fix git diff when core.autocrlf is enabled (helix-editor#4995)

Author: pascalkuthe

helix-vcs/src/git.rs

@@ -17,14 +17,17 @@ impl Git {
         // custom open options
         let mut git_open_opts_map = git::sec::trust::Mapping::<git::open::Options>::default();
 
-        // don't use the global git configs (not needed)
+        // On windows various configuration options are bundled as part of the installations
+        // This path depends on the install location of git and therefore requires some overhead to lookup
+        // This is basically only used on windows and has some overhead hence it's disabled on other platforms.
+        // `gitoxide` doesn't use this as default
         let config = git::permissions::Config {
-            system: false,
-            git: false,
-            user: false,
+            system: true,
+            git: true,
+            user: true,
             env: true,
             includes: true,
-            git_binary: false,
+            git_binary: cfg!(windows),
         };
         // change options for config permissions without touching anything else
         git_open_opts_map.reduced = git_open_opts_map.reduced.permissions(git::Permissions {
@@ -61,7 +64,29 @@ impl DiffProvider for Git {
         let file_oid = find_file_in_commit(&repo, &head, file)?;
 
         let file_object = repo.find_object(file_oid).ok()?;
-        Some(file_object.detach().data)
+        let mut data = file_object.detach().data;
+        // convert LF to CRLF if configured to avoid showing every line as changed
+        if repo
+            .config_snapshot()
+            .boolean("core.autocrlf")
+            .unwrap_or(false)
+        {
+            let mut normalized_file = Vec::with_capacity(data.len());
+            let mut at_cr = false;
+            for &byte in &data {
+                if byte == b'\n' {
+                    // if this is a LF instead of a CRLF (last byte was not a CR)
+                    // insert a new CR to generate a CRLF
+                    if !at_cr {
+                        normalized_file.push(b'\r');
+                    }
+                }
+                at_cr = byte == b'\r';
+                normalized_file.push(byte)
+            }
+            data = normalized_file
+        }
+        Some(data)
     }
 }