internals: Add CI test script

We do not currently run the `internals` crate tests in CI. Bad
rust-bitcoin developers, no biscuit.

.github/workflows/rust.yml

@@ -20,7 +20,7 @@ jobs:
           DO_LINT: true
           AS_DEPENDENCY: false
           DO_NO_STD: true
-          DO_FEATURE_MATRIX: true # Currently only used in hashes crate.
+          DO_FEATURE_MATRIX: true
           DO_SCHEMARS_TESTS: true # Currently only used in hashes crate.
         run: ./contrib/test.sh
 
@@ -70,7 +70,7 @@ jobs:
         uses: dtolnay/rust-toolchain@1.41.1
       - name: Running test script
         env:
-          DO_FEATURE_MATRIX: true # Currently only used in hashes crate.
+          DO_FEATURE_MATRIX: true
         run: ./contrib/test.sh
 
   NoStd:

contrib/test.sh

@@ -2,7 +2,7 @@
 
 set -ex
 
-CRATES="bitcoin hashes"
+CRATES="bitcoin hashes internals"
 
 for crate in ${CRATES}
 do

internals/contrib/test.sh

@@ -0,0 +1,54 @@
+#!/bin/sh
+
+set -ex
+
+FEATURES="std alloc"
+
+cargo --version
+rustc --version
+
+# Work out if we are using a nightly toolchain.
+NIGHTLY=false
+if cargo --version | grep nightly >/dev/null; then
+    NIGHTLY=true
+fi
+
+# Make all cargo invocations verbose
+export CARGO_TERM_VERBOSE=true
+
+# Defaults / sanity checks
+cargo build
+cargo test
+
+if [ "$DO_LINT" = true ]
+then
+    cargo clippy --all-features --all-targets -- -D warnings
+fi
+
+if [ "$DO_FEATURE_MATRIX" = true ]; then
+    # No features
+    cargo build --no-default-features
+    cargo test --no-default-features
+
+    # All features
+    cargo build --no-default-features --features="$FEATURES"
+    cargo test --no-default-features --features="$FEATURES"
+
+    # Single features
+    for feature in ${FEATURES}
+    do
+        cargo build --no-default-features --features="$feature"
+        cargo test --no-default-features --features="$feature"
+    done
+fi
+
+# Build the docs if told to (this only works with the nightly toolchain)
+if [ "$DO_DOCSRS" = true ]; then
+    RUSTDOCFLAGS="--cfg docsrs -D warnings -D rustdoc::broken-intra-doc-links" cargo +nightly doc --all-features
+fi
+
+# Build the docs with a stable toolchain, in unison with the DO_DOCSRS command
+# above this checks that we feature guarded docs imports correctly.
+if [ "$DO_DOCS" = true ]; then
+    RUSTDOCFLAGS="-D warnings" cargo +stable doc --all-features
+fi