Use bash strict mode in all CI scripts (#2012)

"Bash strict mode" is a colloquial expression for a set of settings that
makes Bash stricter (safer). See e.g.
https://gist.github.com/robin-a-meade/58d60124b88b60816e8349d1e3938615

TLDR: to avoid errors from being silently ignored, we should set errexit
(exit script on error), nounset (exit script when an undefined variable
is encountered) and pipefail (propagate error codes in pipelines) in all
our scripts.

Unfortunately, `errexit` is in fact not enough to exit when any error
occurs, some errors are swallowed:
https://dev.to/banks/stop-ignoring-errors-in-bash-3co5

Because of this, I changed the whitespace script to gather the files in
a different way (I copied the approach from the clang-format script),
such
that the script will exit when an error occurs, instead of continuing to
run.

The whitespace script was missing a fetch which was causing `git
merge-base` to fail. Maybe our other scripts should also be updated to
only run on changed files.

Interestingly, GitHub already sets `-e` (`errexit`) when running
scripts, but it's best to enforce it in the script itself:

```
Run ./build_tools/github_actions/lint_whitespace_checks.sh
  ./build_tools/github_actions/lint_whitespace_checks.sh
  shell: /usr/bin/bash -e {0}
```

Fixes #2010

.github/workflows/lint.yml

@@ -52,6 +52,7 @@ jobs:
 
       - name: Run Whitespace Checks
         run: |
+          git fetch --no-tags --prune --depth=1 origin "${GITHUB_BASE_REF?}:${GITHUB_BASE_REF?}"
           ./build_tools/github_actions/lint_whitespace_checks.sh
 
   version-checks:

build_tools/github_actions/ci_build_bazel.sh

@@ -12,6 +12,10 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+set -o errexit
+set -o nounset
+set -o pipefail
+
 if [[ $# -ne 0 ]] ; then
   echo "Usage: $0"
   exit 1

build_tools/github_actions/ci_build_cmake.sh

@@ -20,6 +20,10 @@
 # during `ci_configure`, and builds stablehlo in the directory specified
 # by the second argument.
 
+set -o errexit
+set -o nounset
+set -o pipefail
+
 if [[ $# -ne 2 ]] ; then
   echo "Usage: $0 <llvm_build_dir> <stablehlo_build_dir>"
   exit 1

build_tools/github_actions/ci_build_cmake_code_coverage.sh

@@ -12,6 +12,10 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+set -o errexit
+set -o nounset
+set -o pipefail
+
 print_usage() {
   echo "Usage:"
   echo "$0 [-g][-o output_dir] <llvm_build_dir> <stablehlo_build_dir>"

build_tools/github_actions/ci_build_cmake_llvm.sh

@@ -16,6 +16,10 @@
 # This file is similar to build_mlir.sh, but passes different flags for
 # caching in GitHub Actions to improve build speeds.
 
+set -o errexit
+set -o nounset
+set -o pipefail
+
 if [[ $# -ne 2 ]] ; then
   echo "Usage: $0 <path/to/llvm> <build_dir>"
   exit 1

build_tools/github_actions/ci_build_python_wheel.sh

@@ -16,6 +16,7 @@
 # At the moment it only builds a Linux variant of Python wheel for the
 # default python3 version present on the system (set via GitHub action typically)
 # TODO: Incorporate cibuildwheel and build manylinux wheels
+
 set -o errexit
 set -o nounset
 set -o pipefail

build_tools/github_actions/lint_clang_format.sh

@@ -12,14 +12,18 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+set -o errexit
+set -o nounset
+set -o pipefail
+
 print_usage() {
-  echo "Usage: $0 [-fd]"
+  echo "Usage: $0 [-fb]"
   echo "    -f           Auto-fix clang-format issues."
-  echo "    -b <branch>  Base branch name, default to origin/main."
+  echo "    -b <branch>  Base branch name, defaults to main."
 }
 
 FORMAT_MODE='validate'
-BASE_BRANCH="$(git merge-base HEAD origin/main)"
+BASE_BRANCH=main
 while getopts 'fb:' flag; do
   case "${flag}" in
     f) FORMAT_MODE="fix" ;;

build_tools/github_actions/lint_llvm_commit.sh

@@ -12,6 +12,10 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+set -o errexit
+set -o nounset
+set -o pipefail
+
 print_usage() {
   echo "Usage: $0 [-f] <path/to/stablehlo/root>"
   echo "    -f           Auto-fix LLVM commit mismatch."

build_tools/github_actions/lint_markdown.sh

@@ -16,6 +16,10 @@
 # If passing the files as a glob, be sure to wrap in quotes. For more info,
 # see https://github.com/igorshubovych/markdownlint-cli#globbing
 
+set -o errexit
+set -o nounset
+set -o pipefail
+
 if [[ $# -gt 2 ]] ; then
   echo "Usage: $0 [-f] <files|directories|globs>"
   echo "  -f  Autofix markdown issues."

build_tools/github_actions/lint_version.sh

@@ -17,6 +17,10 @@
 # checking if files named stablehlo_legalize_to_vhlo.X_Y_0.mlir and .mlir.bc
 # exist.
 
+set -o errexit
+set -o nounset
+set -o pipefail
+
 ## Setup VERSION variable as global:
 VERSION_H="stablehlo/dialect/Version.h"
 set_version_var() {

build_tools/github_actions/lint_whitespace_checks.sh

@@ -12,13 +12,18 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+set -o errexit
+set -o nounset
+set -o pipefail
+
 print_usage() {
-  echo "Usage: $0 [-f]"
+  echo "Usage: $0 [-fb]"
   echo "    -f           Auto-fix whitespace issues."
+  echo "    -b <branch>  Base branch name, defaults to main."
 }
 
 FORMAT_MODE='validate'
-BASE_BRANCH="$(git merge-base HEAD origin/main)"
+BASE_BRANCH=main
 while getopts 'fb:' flag; do
   case "${flag}" in
     f) FORMAT_MODE="fix" ;;
@@ -34,19 +39,22 @@ if [[ $# -ne 0 ]] ; then
   exit 1
 fi
 
-get_source_files() {
-  git diff "$BASE_BRANCH" HEAD --name-only --diff-filter=d | grep '.*\.cpp$\|.*\.h$\|.*\.md$\|.*\.mlir$\|.*\.sh$\|.*\.td$\|.*\.txt$\|.*\.yml$\|.*\.yaml$'
-}
-echo "Checking whitespace:"
-echo "  $(get_source_files | xargs)"
+echo "Gathering changed files..."
+mapfile -t CHANGED_FILES < <(git diff "$BASE_BRANCH" HEAD --name-only --diff-filter=d | grep '.*\.cpp$\|.*\.h$\|.*\.md$\|.*\.mlir$\|.*\.sh$\|.*\.td$\|.*\.txt$\|.*\.yml$\|.*\.yaml$')
+if (( ${#CHANGED_FILES[@]} == 0 )); then
+  echo "No files to check."
+  exit 0
+fi
+
+echo "${CHANGED_FILES[@]}"
 
 files_without_eof_newline() {
   # shellcheck disable=SC2016
-  get_source_files | xargs -L1 bash -c 'test "$(tail -c 1 "$0")" && echo "$0"'
+  printf "%s\n" "${CHANGED_FILES[@]}" | xargs -L1 bash -c 'test "$(tail -c 1 "$0")" && echo "$0"'
 }
 
 files_with_trailing_whitespace() {
-  get_source_files | xargs -L1 grep -lP '[ \t]+$'
+  printf "%s\n" "${CHANGED_FILES[@]}" | xargs -L1 grep -lP '[ \t]+$'
 }
 
 fix_files_without_eof_newline() {

build_tools/github_actions/llvm_gcov.sh

@@ -12,6 +12,10 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+set -o errexit
+set -o nounset
+set -o pipefail
+
 # This is a helper script used by lcov in
 # ci_build_cmake_code_coverage.sh
 exec llvm-cov-14 gcov "$@"