fix: issue where odd length prefixes did not work

src/main.rs

@@ -21,15 +21,22 @@ use spiral::Spiral;
 
 // Validate prefix is hex or handle special "hook" value.
 fn validate_prefix(prefix: &str) {
-    match hex::decode(&prefix) {
+    // In order to validate as hex the string must be of even length.
+    let normalised_prefix = if prefix.len() % 2 == 0 {
+        String::from(prefix)
+    } else {
+        format!("{}0", prefix)
+    };
+
+    match hex::decode(normalised_prefix) {
         Ok(_) => {}
         Err(_) => {
             if prefix == "hook" {
                 git::create_post_commit_hook().expect("Failed to create git hook");
                 process::exit(0);
             }
 
-            println!(
+            eprintln!(
                 "The prefix must only contain hex characters! Got: {}",
                 &prefix,
             );

tests_integration/test_prefix.rs

@@ -23,6 +23,37 @@ Patching last commit to include new hash... Success!
     assert_eq!(expected, stdout);
 });
 
+// Works with a prefix of odd length.
+gashtest!(allows_prefixes_of_odd_length, |mut tcmd: TestCommand| {
+    let odd_prefix = "123";
+    let stdout = tcmd.args(&[odd_prefix]).stdout();
+
+    let expected = format!(
+        "\
+Searching for hash with prefix {prefix}
+Found hash {prefix}{hash}
+Patching last commit to include new hash... Success!
+",
+        prefix = odd_prefix,
+        hash = &git_last_hash(tcmd.dir())[odd_prefix.len()..]
+    );
+
+    assert_eq!(expected, stdout);
+});
+
+// Does not allow non-hex characters as prefix.
+gashtest!(does_not_allow_non_hex_chars, |mut tcmd: TestCommand| {
+    let bad_prefix = "hello";
+    let stderr = tcmd.args(&[bad_prefix]).stderr();
+    let expected = format!(
+        "\
+The prefix must only contain hex characters! Got: {}
+",
+        bad_prefix
+    );
+    assert_eq!(expected, stderr);
+});
+
 // Does not patch the commit with --dry-run.
 gashtest!(dry_run_long_prefix, |mut tcmd: TestCommand| {
     let hash_before = git_last_hash(tcmd.dir());