[Buildroot] [PATCH v2] support/download/cargo-post-process: cargo output for vendor config

[Simon Richter]

Use the output of `cargo vendor` to generate the vendor configuration.

Fixes the need to patch the generated configuration if there are
non-crates.io dependencies.

Note:
  `cargo vendor` currently prints a newline before it prints the
  needed configuration.

  This is fixed in +nightly, will end up in +stable soon and must
  be considered when updating cargo.
  See: https://github.com/rust-lang/cargo/pull/11273

  Until then it is needed to remove this first line to make sure
  that the contents of .cargo/config will be the same as they were
  generated with the earlier version of the script. Thus, the
  hashes of the packages that use this script remain the same.

Signed-off-by: Simon Richter <simon.richter at ptwdosimetry.com>
---
 support/download/cargo-post-process | 26 +++++++++++++++++++-------
 1 file changed, 19 insertions(+), 7 deletions(-)

diff --git a/support/download/cargo-post-process b/support/download/cargo-post-process
index a4a4718a2a..186e9eb69b 100755
--- a/support/download/cargo-post-process
+++ b/support/download/cargo-post-process
@@ -1,6 +1,7 @@
 #!/usr/bin/env bash
 
 set -e
+set -o pipefail
 
 . "${0%/*}/helpers"
 
@@ -22,17 +23,28 @@ post_process_unpack "${base_name}" "${output}"
 
 # Do the Cargo vendoring
 pushd "${base_name}" > /dev/null
-cargo vendor --manifest-path ${BR_CARGO_MANIFEST_PATH-Cargo.toml} --locked VENDOR
 
 # Create the local .cargo/config with vendor info
+#
+# The first line of the output to stdout is empty.
+# So skip it to have the file start with the vendoring
+# configuration (`tail --lines=+2`).
+#
+# NOTE:
+#   There is  a patch for cargo to remove the first empty line:
+#   See: https://github.com/rust-lang/cargo/pull/11273
+#
+#   The patch already landed in +nightly and will end up
+#   in +stable soon.
+#
+# ->  When updating rust/cargo, the call to `tail` must be removed.
+#
 mkdir -p .cargo/
-cat <<EOF >.cargo/config
-[source.crates-io]
-replace-with = "vendored-sources"
+cargo vendor \
+    --manifest-path ${BR_CARGO_MANIFEST_PATH-Cargo.toml} \
+    --locked VENDOR \
+    | tail --lines=+2 | tee .cargo/config
 
-[source.vendored-sources]
-directory = "VENDOR"
-EOF
 popd > /dev/null
 
 post_process_repack "$(pwd)" "${base_name}" "${output}"
-- 
2.38.1