docs: update

README.md

@@ -1070,7 +1070,8 @@ Alternative to the `dirname` command.
 ```sh
 dirname() {
     # Usage: dirname "path"
-    dir=${1%%/}
+    dir=${1:-.}
+    dir=${dir%%${dir##*[!/]}}
     [[ "${dir##*/*}" ]] && dir=.
     dir=${dir%/*}
 

manuscript/chapter2.txt

@@ -5,6 +5,8 @@
 Enabling `extdebug` allows access to the `BASH_ARGV` array which stores
 the current function’s arguments in reverse.
 
+**CAVEAT**: Requires `shopt -s compat44` in `bash` 5.0+.
+
 **Example Function:**
 
 ```sh
@@ -41,6 +43,8 @@ allows us to effectively remove array duplicates.
 
 **CAVEAT:** Requires `bash` 4+
 
+**CAVEAT:** List order may not stay the same.
+
 **Example Function:**
 
 ```sh

manuscript/chapter5.txt

@@ -9,7 +9,8 @@ Alternative to the `dirname` command.
 ```sh
 dirname() {
     # Usage: dirname "path"
-    dir=${1%%/}
+    dir=${1:-.}
+    dir=${dir%%${dir##*[!/]}}
     [[ "${dir##*/*}" ]] && dir=.
     dir=${dir%/*}
 

test.sh

@@ -129,6 +129,21 @@ test_dirname() {
 
     result="$(dirname "something/")"
     assert_equals "$result" "."
+
+    result="$(dirname "//")"
+    assert_equals "$result" "/"
+
+    result="$(dirname "//foo")"
+    assert_equals "$result" "/"
+
+    result="$(dirname "")"
+    assert_equals "$result" "."
+
+    result="$(dirname "something//")"
+    assert_equals "$result" "."
+
+    result="$(dirname "something/////////////////////")"
+    assert_equals "$result" "."
 }
 
 test_basename() {