ENH: Add SKIP_RULE_DEPENDS option for add_custom_command()

  - Allows make rules to be created with no dependencies.
  - Such rules will not re-run even if the commands themselves change.
  - Useful to create rules that run only if the output is missing.

1 files changed, 7 insertions, 1 deletions

diff --git a/Source/cmAddCustomCommandCommand.h b/Source/cmAddCustomCommandCommand.h
index 7829b61..b58a398 100644
--- a/Source/cmAddCustomCommandCommand.h
+++ b/Source/cmAddCustomCommandCommand.h
@@ -71,7 +71,7 @@ public:
       "                     COMMAND command1 [ARGS] [args1...]\n"
       "                     [COMMAND command2 [ARGS] [args2...] ...]\n"
       "                     [MAIN_DEPENDENCY depend]\n"
-      "                     [DEPENDS [depends...]]\n"
+      "                     [DEPENDS [depends...]] [SKIP_RULE_DEPENDS]\n"
       "                     [IMPLICIT_DEPENDS <lang1> depend1 ...]\n"
       "                     [WORKING_DIRECTORY dir]\n"
       "                     [COMMENT comment] [VERBATIM] [APPEND])\n"
@@ -134,6 +134,12 @@ public:
       "created as a file on disk it should be marked as SYMBOLIC with "
       "SET_SOURCE_FILES_PROPERTIES.\n"
 
+      "The SKIP_RULE_DEPENDS option prevents the custom build rule from "
+      "having a dependency on itself.  This prevents the rule from running "
+      "again just because the command changed but is useful to create "
+      "rules that have absolutely no dependencies.  Such rules run only "
+      "when the output file is missing.\n"
+
       "The IMPLICIT_DEPENDS option requests scanning of implicit "
       "dependencies of an input file.  The language given specifies the "
       "programming language whose corresponding dependency scanner should "