Added test for specifying git command

vergen/tests/git_output.rs

@@ -572,4 +572,22 @@ cargo:rerun-if-env-changed=SOURCE_DATE_EPOCH
         env::remove_var("VERGEN_GIT_SHA");
         Ok(())
     }
+
+    #[cfg(feature = "gitcl")]
+    #[test]
+    #[serial_test::serial]
+    fn git_cmd_override_works() -> Result<()> {
+        let mut stdout_buf = vec![];
+        let failed = EmitBuilder::builder()
+            .all_git()
+            .git_cmd(Some("git -v"))
+            .emit_to(&mut stdout_buf)?;
+        let output = String::from_utf8_lossy(&stdout_buf);
+        if repo_exists().is_ok() && !failed {
+            assert!(GIT_REGEX_INST.is_match(&output));
+        } else {
+            assert_eq!(ALL_IDEM_OUTPUT, output);
+        }
+        Ok(())
+    }
 }