Allow Rust build using locally supplied crates or crates.io

This adds a couple of configure commands to control whether we're
requiring all dependencies to be available locally (default) or not
(--enable-cargo-online-mode). When building from a tarball, we require
the RUST_DEPENDENCIES variable to point to the local repository of
crates. This also adds src/ext/rust as a git submodule that contains
such a local repository for easy setup.

src/rust/.cargo/config.in

@@ -0,0 +1,8 @@
+[source]
+
+@RUST_DL@ [source.crates-io]
+@RUST_DL@ registry = 'https://github.com/rust-lang/crates.io-index'
+@RUST_DL@ replace-with = 'vendored-sources'
+
+@RUST_DL@ [source.vendored-sources]
+@RUST_DL@ directory = '@RUST_DEPENDENCIES@'

src/rust/Cargo.toml

@@ -5,10 +5,3 @@ members = ["tor_util"]
 debug = true
 panic = "abort"
 
-[source.crates-io]
-registry = 'https://github.com/rust-lang/crates.io-index'
-replace-with = 'vendored-sources'
-
-[source.vendored-sources]
-directory = 'vendor'
-

src/rust/include.am

@@ -2,4 +2,5 @@ include src/rust/tor_util/include.am
 
 EXTRA_DIST +=\
 	src/rust/Cargo.toml \
-	src/rust/Cargo.lock
+	src/rust/Cargo.lock \
+	src/rust/.cargo/config.in

src/rust/tor_util/include.am

@@ -7,6 +7,7 @@ EXTRA_DIST +=\
 src/rust/target/release/libtor_util.a: FORCE
 	( cd "$(abs_top_srcdir)/src/rust/tor_util" ; \
 		CARGO_TARGET_DIR="$(abs_top_builddir)/src/rust/target" \
+		HOME="$(abs_top_builddir)/src/rust" \
 		$(CARGO) build --release --quiet $(CARGO_ONLINE) )
 
 FORCE:

src/test/include.am

@@ -5,6 +5,7 @@ TESTS_ENVIRONMENT = \
 	export PYTHON="$(PYTHON)"; \
 	export SHELL="$(SHELL)"; \
 	export abs_top_srcdir="$(abs_top_srcdir)"; \
+	export abs_top_builddir="$(abs_top_builddir)"; \
 	export builddir="$(builddir)"; \
 	export TESTING_TOR_BINARY="$(TESTING_TOR_BINARY)"; \
 	export CARGO="$(CARGO)"; \

src/test/test_rust.sh

@@ -7,7 +7,7 @@ exitcode=0
 
 for crate in $crates; do
     cd "${abs_top_srcdir:-.}/src/rust/${crate}"
-    "${CARGO:-cargo}" test ${CARGO_ONLINE-"--frozen"} || exitcode=1
+    CARGO_TARGET_DIR="${abs_top_builddir}/src/rust/target" HOME="${abs_top_builddir}/src/rust" "${CARGO:-cargo}" test ${CARGO_ONLINE-"--frozen"} || exitcode=1
 done
 
 exit $exitcode