make date-check more easy to use

One could not run it like the following, for the would be a panic:

    cargo run --manifest-path ci/date-check/Cargo.toml .

Author: tshepang

Diff for: ci/date-check/src/main.rs

@@ -1,9 +1,5 @@
 use std::{
-    collections::BTreeMap,
-    convert::TryInto as _,
-    env, fmt, fs,
-    path::{Path, PathBuf},
-    str::FromStr,
+    collections::BTreeMap, convert::TryInto as _, env, fmt, fs, path::PathBuf, str::FromStr,
 };
 
 use chrono::{Datelike as _, Month, TimeZone as _, Utc};
@@ -127,7 +123,6 @@ fn main() {
     let root_dir = env::args()
         .nth(1)
         .expect("expect root Markdown directory as CLI argument");
-    let root_dir_path = Path::new(&root_dir);
     let glob_pat = format!("{}/**/*.md", root_dir);
     let today_chrono = Utc::today();
     let current_month = Date {
@@ -165,10 +160,7 @@ fn main() {
         println!();
 
         for (path, dates) in dates_by_file {
-            println!(
-                "- [ ] {}",
-                path.strip_prefix(&root_dir_path).unwrap().display()
-            );
+            println!("- [ ] {}", path.display());
             for (line, date) in dates {
                 println!("  - [ ] line {}: {}", line, date);
             }