fix some nits (#2034)

rework maybe_cargo_install(), renamed to cargo_install_unless, updated to take a command to attempt

book/build.sh

@@ -8,25 +8,16 @@ _() {
   "$@"
 }
 
-maybe_cargo_install() {
-  declare cmd=$1
-  declare crate=$2
+cargo_install_unless() {
+  declare crate=$1
+  shift
 
-  if [[ -z $crate ]]; then
-    crate=$cmd
-  fi
-
-  set +e
-  "$cmd" --help > /dev/null 2>&1
-  declare exitcode=$?
-  set -e
-  if [[ $exitcode -ne 0 ]]; then
+  "$@" > /dev/null 2>&1 || \
     _ cargo install "$crate"
-  fi
 }
 
 export PATH=$CARGO_HOME/bin:$PATH
-maybe_cargo_install mdbook
-maybe_cargo_install svgbob svgbob_cli
+cargo_install_unless mdbook mdbook --help
+cargo_install_unless svgbob_cli svgbob --help
 
 _ make

ci/audit.sh

@@ -15,19 +15,16 @@ _() {
   "$@"
 }
 
-maybe_cargo_install() {
-  for cmd in "$@"; do
-    set +e
-    cargo "$cmd" --help > /dev/null 2>&1
-    declare exitcode=$?
-    set -e
-    if [[ $exitcode -eq 101 ]]; then
-      _ cargo install cargo-"$cmd"
-    fi
-  done
+cargo_install_unless() {
+  declare crate=$1
+  shift
+
+  "$@" > /dev/null 2>&1 || \
+    _ cargo install "$crate"
 }
 
-maybe_cargo_install audit tree
+cargo_install_unless cargo-audit cargo audit --version
+cargo_install_unless cargo-tree cargo tree --version
 
 _ cargo tree
 _ cargo audit

ci/test-nightly.sh

@@ -15,19 +15,15 @@ _() {
 # Uncomment this to run nightly test suit
 # _ cargo test --verbose --features=unstable -- --test-threads=1
 
-maybe_cargo_install() {
-  for cmd in "$@"; do
-    set +e
-    cargo "$cmd" --help > /dev/null 2>&1
-    declare exitcode=$?
-    set -e
-    if [[ $exitcode -eq 101 ]]; then
-      _ cargo install cargo-"$cmd"
-    fi
-  done
+cargo_install_unless() {
+  declare crate=$1
+  shift
+
+  "$@" > /dev/null 2>&1 || \
+    _ cargo install "$crate"
 }
 
-maybe_cargo_install cov
+cargo_install_unless cargo-cov cargo cov --help
 
 # Generate coverage data and report via unit-test suite.
 _ cargo cov clean