feat: prepend $pkgdir to avoid user hassle

Cargo.toml

@@ -27,4 +27,4 @@ panic = "abort"
 
 [package.metadata.aur]
 # depends = ["blah"]
-# files = [[".github/dependabot.yml", "$pkgdir/usr/local/share/cargo-aur/dependabot.yml"]]
+# files = [[".github/dependabot.yml", "/usr/local/share/cargo-aur/dependabot.yml"]]

README.md

@@ -90,7 +90,7 @@ filesystem. So this:
 
 ```toml
 [package.metadata.aur]
-files = [["path/to/local/foo.txt", "$pkgdir/usr/local/share/your-app/foo.txt"]]
+files = [["path/to/local/foo.txt", "/usr/local/share/your-app/foo.txt"]]
 ```
 
 will result in this:

src/error.rs

@@ -1,6 +1,6 @@
 //! Errors that can occur in this application.
 
-use std::fmt::Display;
+use std::{fmt::Display, path::PathBuf};
 
 pub(crate) enum Error {
     IO(std::io::Error),
@@ -9,6 +9,7 @@ pub(crate) enum Error {
     Utf8OsString,
     MissingMuslTarget,
     MissingLicense,
+    TargetNotAbsolute(PathBuf),
 }
 
 impl Display for Error {
@@ -25,6 +26,9 @@ impl Display for Error {
             Error::MissingLicense => {
                 write!(f, "Missing LICENSE file. See https://choosealicense.com/")
             }
+            Error::TargetNotAbsolute(p) => {
+                write!(f, "Target filepath is not absolute: {}", p.display())
+            }
         }
     }
 }

src/lib.rs

@@ -163,5 +163,5 @@ pub struct AUR {
     #[serde(default)]
     optdepends: Vec<String>,
     #[serde(default)]
-    pub files: Vec<(String, String)>,
+    pub files: Vec<(PathBuf, PathBuf)>,
 }

src/main.rs

@@ -239,7 +239,16 @@ where
 
     if let Some(aur) = package.metadata.as_ref().and_then(|m| m.aur.as_ref()) {
         for (source, target) in aur.files.iter() {
-            writeln!(file, "    install -Dm644 \"{}\" \"{}\"", source, target)?;
+            if target.has_root().not() {
+                return Err(Error::TargetNotAbsolute(target.to_path_buf()));
+            } else {
+                writeln!(
+                    file,
+                    "    install -Dm644 \"{}\" \"$pkgdir{}\"",
+                    source.display(),
+                    target.display()
+                )?;
+            }
         }
     }