Merge #689: ci: shellcheck checks

926bb05 ci: shellcheck checks (Jose Storopoli)

Pull request description:

  Following rust-bitcoin/rust-bitcoin#2762,
  adding CI shellcheck cheks here as well.

  I also did all fixes that I could find with

  ```bash
  shellcheck **/*.sh
  ```

  If I've missed any please let me know.

ACKs for top commit:
  apoelstra:
    ACK 926bb05
  tcharding:
    ACK 926bb05

Tree-SHA512: 1eb32b6d1f3008a03b70995c3b936921bad9a2ea7f329133e704fd9b4eb9bd7ec5cac7cd5e4a4a2ceff83eec03c785478cb1de37922b5b9d7787c907040876d4

Author: apoelstra

.github/workflows/shellcheck.yml

@@ -0,0 +1,16 @@
+
+name: Shellcheck
+on:
+  pull_request:
+    branches:
+      - master
+jobs:
+  shellcheck:
+    name: Shellcheck
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+    - name: Run ShellCheck
+      uses: ludeeus/action-shellcheck@2.0.0
+      env:
+        SHELLCHECK_OPTS: -x # allow outside sources

embedded/scripts/env.sh

@@ -1,2 +1,4 @@
+# we don't want shebangs in env.sh, disable shellcheck warning
+# shellcheck disable=SC2148
 export RUSTFLAGS="-C link-arg=-Tlink.x"
 export CARGO_TARGET_THUMBV7M_NONE_EABI_RUNNER="qemu-system-arm -cpu cortex-m3 -machine mps2-an385 -nographic -semihosting-config enable=on,target=native -kernel"

fuzz/cycle.sh

@@ -7,7 +7,8 @@
 
 set -e
 REPO_DIR=$(git rev-parse --show-toplevel)
-# shellcheck source=./fuzz-util.sh
+# can't find the file because of the ENV var
+# shellcheck source=/dev/null
 source "$REPO_DIR/fuzz/fuzz-util.sh"
 
 while :

fuzz/fuzz.sh

@@ -3,7 +3,8 @@ set -ex
 
 REPO_DIR=$(git rev-parse --show-toplevel)
 
-# shellcheck source=./fuzz-util.sh
+# can't find the file because of the ENV var
+# shellcheck source=/dev/null
 source "$REPO_DIR/fuzz/fuzz-util.sh"
 
 # Check that input files are correct Windows file names

fuzz/generate-files.sh

@@ -4,7 +4,8 @@ set -e
 
 REPO_DIR=$(git rev-parse --show-toplevel)
 
-# shellcheck source=./fuzz-util.sh
+# can't find the file because of the ENV var
+# shellcheck source=/dev/null
 source "$REPO_DIR/fuzz/fuzz-util.sh"
 
 # 1. Generate fuzz/Cargo.toml