string(TIMESTAMP ...): add '%a' and '%b' format specifiers

%b: Abbreviated month name (e.g. Oct).
%a: Abbreviated weekday name (e.g. Fri).

Help/command/string.rst

@@ -278,12 +278,14 @@ specifiers:
    %I        The hour on a 12-hour clock (01-12).
    %j        The day of the current year (001-366).
    %m        The month of the current year (01-12).
+   %b        Abbreviated month name (e.g. Oct).
    %M        The minute of the current hour (00-59).
    %s        Seconds since midnight (UTC) 1-Jan-1970 (UNIX time).
    %S        The second of the current minute.
              60 represents a leap second. (00-60)
    %U        The week number of the current year (00-53).
    %w        The day of the current week. 0 is Sunday. (0-6)
+   %a        Abbreviated weekday name (e.g. Fri).
    %y        The last two digits of the current year (00-99)
    %Y        The current year.
 

Source/cmTimestamp.cxx

@@ -123,6 +123,8 @@ std::string cmTimestamp::AddTimestampComponent(char flag,
   formatString += flag;
 
   switch (flag) {
+    case 'a':
+    case 'b':
     case 'd':
     case 'H':
     case 'I':

Tests/CMakeTests/String-TIMESTAMP-MonthWeekNames.cmake

@@ -0,0 +1,11 @@
+string(TIMESTAMP output "%a;%b")
+message("~${output}~")
+
+list(LENGTH output output_length)
+
+set(expected_output_length 2)
+
+if(NOT output_length EQUAL ${expected_output_length})
+    message(FATAL_ERROR "expected ${expected_output_length} entries in output "
+        "with all specifiers; found ${output_length}")
+endif()

Tests/CMakeTests/StringTest.cmake.in

@@ -36,6 +36,8 @@ set(TIMESTAMP-IncompleteSpecifier-RESULT 0)
 set(TIMESTAMP-IncompleteSpecifier-STDERR "~foobar%~")
 set(TIMESTAMP-AllSpecifiers-RESULT 0)
 set(TIMESTAMP-AllSpecifiers-STDERR "~[0-9]+(;[0-9]+)*~")
+set(TIMESTAMP-MonthWeekNames-RESULT 0)
+set(TIMESTAMP-MonthWeekNames-STDERR "~[^%]+;[^%]+~")
 set(TIMESTAMP-UnixTime-RESULT 0)
 set(TIMESTAMP-UnixTime-STDERR "~[1-9][0-9]+~")
 
@@ -60,6 +62,7 @@ check_cmake_test(String
   TIMESTAMP-UnknownSpecifier
   TIMESTAMP-IncompleteSpecifier
   TIMESTAMP-AllSpecifiers
+  TIMESTAMP-MonthWeekNames
   TIMESTAMP-UnixTime
   )