feat: Use Unix-style slash on Windows (#119)

Prior to this change, starship would use inconsistent slashes when displaying the working directory. With this change, starship uses Unix-style slashes on all platforms. This is consistent with the Git Bash and Cygwin prompts on Windows.

src/modules/directory.rs

@@ -1,4 +1,5 @@
 use ansi_term::Color;
+use path_slash::PathExt;
 use std::path::Path;
 
 use super::{Context, Module};
@@ -51,25 +52,43 @@ pub fn module<'a>(context: &'a Context) -> Option<Module<'a>> {
 /// `top_level_replacement`.
 fn contract_path(full_path: &Path, top_level_path: &Path, top_level_replacement: &str) -> String {
     if !full_path.starts_with(top_level_path) {
-        return full_path.to_str().unwrap().to_string();
+        return replace_c_dir(full_path.to_slash().unwrap());
     }
 
     if full_path == top_level_path {
-        return top_level_replacement.to_string();
+        return replace_c_dir(top_level_replacement.to_string());
     }
 
     format!(
         "{replacement}{separator}{path}",
         replacement = top_level_replacement,
         separator = "/",
-        path = full_path
-            .strip_prefix(top_level_path)
-            .unwrap()
-            .to_str()
-            .unwrap()
+        path = replace_c_dir(
+            full_path
+                .strip_prefix(top_level_path)
+                .unwrap()
+                .to_slash()
+                .unwrap()
+        )
     )
 }
 
+/// Replaces "C://" with "/c/" within a Windows path
+///
+/// On non-Windows OS, does nothing
+#[cfg(target_os = "windows")]
+fn replace_c_dir(path: String) -> String {
+    return path.replace("C:/", "/c");
+}
+
+/// Replaces "C://" with "/c/" within a Windows path
+///
+/// On non-Windows OS, does nothing
+#[cfg(not(target_os = "windows"))]
+fn replace_c_dir(path: String) -> String {
+    return path;
+}
+
 /// Truncate a path to only have a set number of path components
 ///
 /// Will truncate a path to only show the last `length` components in a path.
@@ -110,6 +129,46 @@ mod tests {
         assert_eq!(output, "rocket-controls/src");
     }
 
+    #[test]
+    #[cfg(target_os = "windows")]
+    fn contract_windows_style_home_directory() {
+        let full_path = Path::new("C:\\Users\\astronaut\\schematics\\rocket");
+        let home = Path::new("C:\\Users\\astronaut");
+
+        let output = contract_path(full_path, home, "~");
+        assert_eq!(output, "~/schematics/rocket");
+    }
+
+    #[test]
+    #[cfg(target_os = "windows")]
+    fn contract_windows_style_repo_directory() {
+        let full_path = Path::new("C:\\Users\\astronaut\\dev\\rocket-controls\\src");
+        let repo_root = Path::new("C:\\Users\\astronaut\\dev\\rocket-controls");
+
+        let output = contract_path(full_path, repo_root, "rocket-controls");
+        assert_eq!(output, "rocket-controls/src");
+    }
+
+    #[test]
+    #[cfg(target_os = "windows")]
+    fn contract_windows_style_no_top_level_directory() {
+        let full_path = Path::new("C:\\Some\\Other\\Path");
+        let top_level_path = Path::new("C:\\Users\\astronaut");
+
+        let output = contract_path(full_path, top_level_path, "~");
+        assert_eq!(output, "/c/Some/Other/Path");
+    }
+
+    #[test]
+    #[cfg(target_os = "windows")]
+    fn contract_windows_style_root_directory() {
+        let full_path = Path::new("C:\\");
+        let top_level_path = Path::new("C:\\Users\\astronaut");
+
+        let output = contract_path(full_path, top_level_path, "~");
+        assert_eq!(output, "/c");
+    }
+
     #[test]
     fn truncate_smaller_path_than_provided_length() {
         let path = "~/starship";