Add Bash completion script (#60)

* Add completion script
* Add introspection

test/115_accept_introspect.bats

@@ -0,0 +1,99 @@
+load common
+load_fixtures
+status=;output=; #; populated by bats run()
+
+function count_introspect() {
+  local category="$1"
+  local expected_status="$2"
+  local expected_words="$3"
+  local expected_regex="$4"
+
+  run "${T_YADM_Y[@]}" introspect "$category"
+  local output_words
+  output_words=$(wc -w <<< "$output")
+
+  if [ "$status" -ne "$expected_status" ]; then
+    echo "ERROR: Unexpected exit code (expected $expected_status, got $status)"
+    return 1;
+  fi
+
+  if [ "$output_words" -ne "$expected_words" ]; then
+    echo "ERROR: Unexpected number of output words (expected $expected_words, got $output_words)"
+    return 1;
+  fi
+
+  if [ -n "$expected_regex" ]; then
+    if [[ ! "$output" =~ $expected_regex ]]; then
+      echo "OUTPUT:$output"
+      echo "ERROR: Output does not match regex: $expected_regex"
+      return 1;
+    fi
+  fi
+
+}
+
+@test "Command 'introspect' (no category)" {
+  echo "
+    When 'introspect' command is provided,
+      And no category is provided
+        Produce no output
+        Exit with 0
+  "
+
+  count_introspect "" 0 0
+}
+
+@test "Command 'introspect' (invalid category)" {
+  echo "
+    When 'introspect' command is provided,
+      And an invalid category is provided
+        Produce no output
+        Exit with 0
+  "
+
+  count_introspect "invalid_cat" 0 0
+}
+
+@test "Command 'introspect' (commands)" {
+  echo "
+    When 'introspect' command is provided,
+      And category 'commands' is provided
+        Produce command list
+        Exit with 0
+  "
+
+  count_introspect "commands" 0 15 'version'
+}
+
+@test "Command 'introspect' (configs)" {
+  echo "
+    When 'introspect' command is provided,
+      And category 'configs' is provided
+        Produce switch list
+        Exit with 0
+  "
+
+  count_introspect "configs" 0 11 'yadm\.auto-alt'
+}
+
+@test "Command 'introspect' (repo)" {
+  echo "
+    When 'introspect' command is provided,
+      And category 'repo' is provided
+        Output repo
+        Exit with 0
+  "
+
+  count_introspect "repo" 0 1 "$T_DIR_REPO"
+}
+
+@test "Command 'introspect' (switches)" {
+  echo "
+    When 'introspect' command is provided,
+      And category 'switches' is provided
+        Produce switch list
+        Exit with 0
+  "
+
+  count_introspect "switches" 0 7 '--yadm-dir'
+}