External: enhanced arguments. Internal: cleanup + find difftool

.gitignore

@@ -1,2 +1,17 @@
 *.received*
 bash/failing-test.approved
+
+# macOS
+.DS_Store
+.DS_Store?
+._*
+.AppleDouble
+.LSOverride
+.Spotlight-V100
+.Trashes
+.DocumentRevisions-V100
+.fseventsd
+.TemporaryItems
+.VolumeIcon.icns
+.com.apple.timemachine.donotpresent
+__MACOSX/

TODO.md

@@ -0,0 +1,55 @@
+# Todo
+
+- diff-tool selection is consistent with `git help difftool`
+- Command line args are consistent with `git dif`
+  Use -t and --tool, NOT -d
+  See: git difftool --tool-help
+
+# Starter code
+
+```bash
+get_git_difftool() {
+    # Check if --tool argument is provided in command line arguments
+    while [[ $# -gt 0 ]]; do
+        case "$1" in
+            -t|--tool)
+                echo "$2"
+                return 0
+                ;;
+            *) shift ;;
+        esac
+    done
+
+    # Check if GIT_DIFF_TOOL environment variable is set
+    if [[ -n "$GIT_DIFF_TOOL" ]]; then
+        echo "$GIT_DIFF_TOOL"
+        return 0
+    fi
+
+    # Fallback to the configured diff.tool in git config
+    git_config_tool="$(git config --get diff.tool)"
+    if [[ -n "$git_config_tool" ]]; then
+        echo "$git_config_tool"
+        return 0
+    fi
+
+    # Default return if no tool is set (to avoid empty return)
+    echo "default-diff-tool"  # Replace this with the actual default tool if needed
+}
+```
+
+## Emacs
+
+;; Local Variables:
+;; eval: (apheleia-mode nil)
+;; eval: (apheleia-mode nil)
+
+;; eval: (apheleia-mode +1)
+;; eval: (apheleia-mode 0)
+;; eval: (apheleia-mode -1)
+
+;; eval: (bound-and-true-p aphelia-mode)
+;; eval: (apheleia-mode)
+
+;; eval: (apheleia-mode-with-elisp-conventions nil)
+;; End:

bash/test.sh

@@ -1,10 +1,46 @@
 #!/bin/bash
 
-echo "test: pass"
-./verify.sh -t test1 <<< "test 1 approves this message
+function test1() {
+	test_name="${FUNCNAME[0]}"
+	echo "test: pass"
+	./verify.sh -t "$test_name" <<<"test 1 approves this message
 line 2"
-echo ""
+	echo ""
+}
 
-echo "test: fails and triggers diff tool"
-./verify.sh -t test3 -d diff <<< "test 3 receives this input"
-echo ""
+function test2() {
+	true
+}
+
+function test3() {
+	test_name="${FUNCNAME[0]}"
+	echo "test: fails and triggers diff tool"
+	./verify.sh -t "$test_name" -d diff <<<"test 3 receives this input"
+	echo ""
+}
+
+function test4() {
+	test_name="${FUNCNAME[0]}"
+	./verify.sh -d meld <<<"Input to test without a name"
+}
+
+function test_diff_tool_selection() {
+	test_name="${FUNCNAME[0]}"
+	cat <<DIFF_TOOL_SELECTION | ./verify.sh -t "$test_name"
+# Logic for diff tool
+# 1. --tool argument takes top priority.
+# 2. If no --tool is specified, GIT_DIFF_TOOL is checked next.
+# 3. If GIT_DIFF_TOOL is unset, git config --get diff.tool is used.
+# 4. If neither is set, Git falls back to its internal diff.
+DIFF_TOOL_SELECTION
+}
+
+function test_all() {
+	test1
+	test2
+	test3
+	test4
+	test_diff_tool_selection
+}
+
+test_all

bash/test_diff_tool_selection.approved

@@ -0,0 +1,5 @@
+# Logic for diff tool
+# 1. --tool argument takes top priority.
+# 2. If no --tool is specified, GIT_DIFF_TOOL is checked next.
+# 3. If GIT_DIFF_TOOL is unset, git config --get diff.tool is used.
+# 4. If neither is set, Git falls back to its internal diff.

bash/unspecified_test_name.approved

@@ -0,0 +1 @@
+Input to test without a name

bash/verify.sh

@@ -1,39 +1,97 @@
 #!/bin/bash
+set -euo pipefail
 
-default_diff_tool="code --diff"
-diff_tool=$default_diff_tool
+true <<TODO
+See:  
+    - git config --get diff.tool
+    - git difftool
+    - git difftool --no-index
+TODO
 
-while getopts ":r:t:d:" opt; do
+git_difftool="$(git config --get diff.tool)"
+vs_code_path=$(command -v code)
+
+if [[ -n "${git_difftool}" ]] && command -v "${git_difftool}"; then
+    difftool="git difftool --tool ${git_difftool} --no-index"
+elif [[ -n "${vs_code_path}" ]]; then
+    difftool="${vs_code_path} --diff"
+else
+    difftool=""
+fi
+
+function warn() {
+    echo "$*" >&2
+}
+
+while getopts ":r:t:d:D" opt; do
     case $opt in
-    d) diff_tool=$OPTARG ;;
-    r) received_text=$OPTARG ;;
-    t) test_name=$OPTARG ;;
-    \?) echo "Invalid option: -$OPTARG" >&2 ;;
+	d) difftool=$OPTARG ;;
+	r) received_text=$OPTARG ;;
+	t) test_name=$OPTARG ;;
+	D) debug_without_compare_and_approve="true" ;;
+	\?) warn "Invalid option: -$OPTARG" ;;
     esac
 done
 
+if [[ "${test_name=}" == '' ]]; then
+    test_name="unspecified_test_name"
+fi
+
 received="$test_name.received"
 approved="$test_name.approved"
 
-if [ "$received_text" == "" ]; then
-    cat - >"$received"
-else
-    echo "$received_text" >"$received"
-fi
+function debug_arguments() {
+    cat <<REPORT
+$0 -d '$difftool' -r '$received_text' -t '$test_name'
+REPORT
+}
+
+function main() {
+    if [ "${received_text=}" == "" ]; then
+	cat - >"$received"
+    else
+	echo "$received_text" >"$received"
+    fi
+
+    touch "$approved"
+
+    if [[ -n "${debug_without_compare_and_approve=}" ]]; then
+	debug_arguments
+    else
+	compare_and_approve "$test_name"
+    fi
+}
+
+function pass() {
+    echo "${1:=unnamed-test} passed"
+}
+
+function fail() {
+    echo "${1:unnamed-test} failed"
+}
+
+function fail_and_diff() {
+    if [ -e /dev/tty ]; then
+	$difftool "$received" "$approved" </dev/tty
+    else
+	$difftool "$received" "$approved"
+    fi
+    false
+}
+
+function pass_and_rm_received() {
+    pass "$1"
+    rm "$received"
+}
+
+function compare_and_approve() {
+    # NB: Following are run in sub-shells to prevent their errors from
+    # terminating this shell. I'm not sure if that's still necessary.
+    if diff -q "$received" "$approved" >/dev/null; then
+	(pass_and_rm_received "$1");
+    else
+	(fail_and_diff "$1")
+    fi
+}
 
-touch "$approved"
-
-diff -q "$received" "$approved" >/dev/null &&
-    (
-        echo "test passed"
-        rm "$received"
-    ) ||
-    (
-        echo "test failed"
-        if [ -t 1 ]; then
-            $diff_tool "$received" "$approved" </dev/tty
-        else
-            $diff_tool "$received" "$approved"
-        fi
-        false
-    )
+main