Add a function to get the shared portion of a path.

src/blog_post/convert.rs

@@ -1,3 +1,4 @@
+use std::path::Component;
 use std::path::Path;
 use std::path::PathBuf;
 
@@ -92,6 +93,17 @@ fn count_shared_steps<A: AsRef<Path>, B: AsRef<Path>>(left: A, right: B) -> usiz
         .unwrap_or_else(|| left.components().count())
 }
 
+#[allow(dead_code)]
+fn get_shared_steps<'a>(left: &'a Path, right: &'a Path) -> impl Iterator<Item = Component<'a>> {
+    let foo: Vec<Component<'_>> = left
+        .components()
+        .zip(right.components())
+        .take_while(|(l, r)| l == r)
+        .map(|(l, _r)| l)
+        .collect();
+    foo.into_iter()
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -106,4 +118,29 @@ mod tests {
             2
         );
     }
+
+    #[test]
+    fn test_get_shared_steps() {
+        assert_eq!(
+            get_shared_steps(Path::new(""), Path::new("")).collect::<PathBuf>(),
+            PathBuf::from("")
+        );
+        assert_eq!(
+            get_shared_steps(Path::new("foo.txt"), Path::new("foo.txt")).collect::<PathBuf>(),
+            PathBuf::from("foo.txt")
+        );
+        assert_eq!(
+            get_shared_steps(Path::new("cat/foo.txt"), Path::new("dog/foo.txt"))
+                .collect::<PathBuf>(),
+            PathBuf::from("")
+        );
+        assert_eq!(
+            get_shared_steps(
+                Path::new("foo/bar/baz/lorem.txt"),
+                Path::new("foo/bar/ipsum/dolar.txt")
+            )
+            .collect::<PathBuf>(),
+            PathBuf::from("foo/bar")
+        );
+    }
 }