rustc: Stop putting hashes in filenames by default

The compiler will no longer insert a hash or version into a filename by default.
Instead, all output is simply based off the crate name being compiled. For
example, a crate name of `foo` would produce the following outputs:

* bin => foo
* rlib => libfoo.rlib
* dylib => libfoo.{so,dylib} or foo.dll
* staticlib => libfoo.a

The old behavior has been moved behind a new codegen flag,
`-C extra-filename=<hash>`. For example, with the "extra filename" of `bar` and
a crate name of `foo`, the following outputs would be generated:

* bin => foo (same old behavior)
* rlib => libfoobar.rlib
* dylib => libfoobar.{so,dylib} or foobar.dll
* staticlib => libfoobar.a

The makefiles have been altered to pass a hash by default to invocations of
`rustc` so all installed rust libraries will have a hash in their filename. This
is done because the standard libraries are intended to be installed into
privileged directories such as /usr/local. Additionally, it involves very few
build system changes!

RFC: 0035-remove-crate-id
[breaking-change]

src/librustc/back/link.rs

@@ -588,18 +588,6 @@ pub fn find_crate_name(sess: Option<&Session>,
     }), None)
 }
 
-pub fn crate_name_hash(sess: &Session, crate_name: &str) -> String {
-    // This calculates CMH as defined above. Note that we don't use the path of
-    // the crate id in the hash because lookups are only done by (name/vers),
-    // not by path.
-    let mut s = Sha256::new();
-    s.input_str(crate_name);
-    for meta in sess.crate_metadata.borrow().iter() {
-        s.input_str(meta.as_slice());
-    }
-    truncated_hash_result(&mut s).as_slice().slice_to(8).to_string()
-}
-
 pub fn build_link_meta(krate: &ast::Crate, name: String) -> LinkMeta {
     let r = LinkMeta {
         crate_name: name,
@@ -880,7 +868,7 @@ pub fn filename_for_input(sess: &Session,
                           crate_type: config::CrateType,
                           name: &str,
                           out_filename: &Path) -> Path {
-    let libname = format!("{}-{}", name, crate_name_hash(sess, name));
+    let libname = format!("{}{}", name, sess.opts.cg.extra_filename);
     match crate_type {
         config::CrateTypeRlib => {
             out_filename.with_filename(format!("lib{}.rlib", libname))

src/librustc/driver/config.rs

@@ -320,6 +320,8 @@ cgoptions!(
          "choose the relocation model to use (llc -relocation-model for details)"),
     metadata: Vec<String> = (Vec::new(), parse_list,
          "metadata to mangle symbol names with"),
+    extra_filename: String = ("".to_string(), parse_string,
+         "extra data to put in each output filename"),
 )
 
 pub fn build_codegen_options(matches: &getopts::Matches) -> CodegenOptions

src/librustc/driver/driver.rs

@@ -903,13 +903,11 @@ pub fn build_output_filenames(input: &Input,
                 None => Path::new(".")
             };
 
-            let mut stem = input.filestem();
-
             // If a crate name is present, we use it as the link name
-            match attr::find_crate_name(attrs) {
-                None => {}
-                Some(name) => stem = name.get().to_string(),
-            }
+           let stem = match attr::find_crate_name(attrs) {
+                None => input.filestem(),
+                Some(name) => name.get().to_string(),
+            };
             OutputFilenames {
                 out_directory: dirpath,
                 out_filestem: stem,