Re-add MSRV exception for ruma-signatures

README.md

@@ -52,6 +52,10 @@ Ruma currently requires Rust 1.50. In general, we will never require beta or
 nightly for crates.io releases of our crates, and we will try to avoid releasing
 crates that depend on features that were only just stabilized.
 
+`ruma-signatures` is an exception: It uses cryptographic libraries that often
+use relatively new features and that we don't want to use outdated versions of.
+It is guarateed to work with whatever is the latest stable version though.
+
 ## License
 
 [MIT](http://opensource.org/licenses/MIT)

xtask/src/ci.rs

@@ -39,15 +39,22 @@ impl CiTask {
 
     fn build_msrv(&self) -> xshell::Result<()> {
         // Check all crates with all features except
-        // * ruma-client (will be tested as part of ruma, don't want to enabled all features)
+        // * ruma (would pull in ruma-signatures)
+        // * ruma-client (tested with default features due to optional HTTP client deps)
+        // * ruma-signatures (MSRV exception)
         // * xtask (no real reason to enforce an MSRV for it)
         cmd!(
             "rustup run {MSRV} cargo check --workspace --all-features
+                --exclude ruma
                 --exclude ruma-client
+                --exclude ruma-signatures
                 --exclude xtask"
         )
         .run()?;
 
+        // Check ruma-client crate with default features
+        cmd!("rustup run {MSRV} cargo check -p ruma-client").run()?;
+
         // Check ruma crate with default features
         cmd!("rustup run {MSRV} cargo check -p ruma").run()
     }