Match the beaviour of meson regarding relative paths in the install directories

Fixes #366

Author: lu-zero

src/cli.rs

@@ -16,27 +16,32 @@ struct Common {
     /// Path to directory where target should be copied to
     #[clap(long = "destdir")]
     destdir: Option<PathBuf>,
-    /// Directory path used to construct default values of
-    /// includedir, libdir, bindir, pkgconfigdir
-    #[clap(long = "prefix")]
-    prefix: Option<PathBuf>,
+    /// Directory path used to construct the values of
+    /// `bindir`, `datarootdir`, `includedir`, `libdir`
+    ///
+    /// If they are absolute the prefix is ignored.
+    #[clap(long = "prefix", default_value = "/usr/local")]
+    prefix: PathBuf,
     /// Path to directory for installing generated library files
-    #[clap(long = "libdir")]
-    libdir: Option<PathBuf>,
+    #[clap(long = "libdir", default_value = "lib")]
+    libdir: PathBuf,
     /// Path to directory for installing generated headers files
-    #[clap(long = "includedir")]
-    includedir: Option<PathBuf>,
+    #[clap(long = "includedir", default_value = "include")]
+    includedir: PathBuf,
     /// Path to directory for installing generated executable files
-    #[clap(long = "bindir")]
-    bindir: Option<PathBuf>,
+    #[clap(long = "bindir", default_value = "bin")]
+    bindir: PathBuf,
     /// Path to directory for installing generated pkg-config .pc files
+    ///
+    /// [default: {libdir}/pkgconfig]
     #[clap(long = "pkgconfigdir")]
     pkgconfigdir: Option<PathBuf>,
-    /// Path to directory for installing read-only data (defaults to {prefix}/share)
-    #[clap(long = "datarootdir")]
-    datarootdir: Option<PathBuf>,
+    /// Path to directory for installing read-only data
+    #[clap(long = "datarootdir", default_value = "share")]
+    datarootdir: PathBuf,
     /// Path to directory for installing read-only application-specific data
-    /// (defaults to {datarootdir})
+    ///
+    /// [default: {datarootdir}]
     #[clap(long = "datadir")]
     datadir: Option<PathBuf>,
     #[clap(long = "dlltool")]

src/install.rs

@@ -289,32 +289,20 @@ impl InstallPaths {
             .get_one::<PathBuf>("prefix")
             .map(PathBuf::from)
             .unwrap_or_else(|| "/usr/local".into());
-        let libdir = args
-            .get_one::<PathBuf>("libdir")
-            .map(PathBuf::from)
-            .unwrap_or_else(|| prefix.join("lib"));
-        let includedir = args
-            .get_one::<PathBuf>("includedir")
-            .map(PathBuf::from)
-            .unwrap_or_else(|| prefix.join("include"));
-        let datarootdir = args
-            .get_one::<PathBuf>("datarootdir")
-            .map(PathBuf::from)
-            .unwrap_or_else(|| prefix.join("share"));
+        let libdir = prefix.join(args.get_one::<PathBuf>("libdir").unwrap());
+        let includedir = prefix.join(args.get_one::<PathBuf>("includedir").unwrap());
+        let datarootdir = prefix.join(args.get_one::<PathBuf>("datarootdir").unwrap());
         let datadir = args
             .get_one::<PathBuf>("datadir")
-            .map(PathBuf::from)
+            .map(|d| prefix.join(d))
             .unwrap_or_else(|| datarootdir.clone());
 
         let subdir_name = PathBuf::from(&capi_config.header.subdirectory);
 
-        let bindir = args
-            .get_one::<PathBuf>("bindir")
-            .map(PathBuf::from)
-            .unwrap_or_else(|| prefix.join("bin"));
+        let bindir = prefix.join(args.get_one::<PathBuf>("bindir").unwrap());
         let pkgconfigdir = args
             .get_one::<PathBuf>("pkgconfigdir")
-            .map(PathBuf::from)
+            .map(|d| prefix.join(d))
             .unwrap_or_else(|| libdir.join("pkgconfig"));
 
         InstallPaths {