Suggestion.diff_command: Diff an index instead of a file

This will enable us to use the `git diff` command with more than one
suggestion at the same time.

We compare the commit of the suggestion with the new index's tree.

And as I write this, I'm realising that we can't diff multiple
suggestions using the same commit because each suggestion has its own
commit.

Need to work out a different way to do this.

1 files changed, 3 insertions, 3 deletions

diff --git a/src/bin/git-sugdiff.rs b/src/bin/git-sugdiff.rs
index 9c7ff1f..362eb15 100644
--- a/src/bin/git-sugdiff.rs
+++ b/src/bin/git-sugdiff.rs
@@ -43,12 +43,12 @@ fn main() {
         &config,
         |suggestion| {
             // TODO: Needs to work for multiple suggestions at once
-            let blob = suggestion.diff_command().unwrap();
+            let tree = suggestion.diff_command().unwrap();
 
             Command::new("git")
                 .arg("diff")
-                .arg(format!("{}:{}", suggestion.commit(), suggestion.path()))
-                .arg(blob.to_string())
+                .arg(suggestion.commit())
+                .arg(tree.to_string())
                 .spawn()
                 .unwrap();
         },