Bash-5.1 patch 6: make sure child processes forked to execute command substitutions are in the right process group

patchlevel.h

@@ -25,6 +25,6 @@
    regexp `^#define[ 	]*PATCHLEVEL', since that's what support/mkversion.sh
    looks for to find the patch level (for the sccs version string). */
 
-#define PATCHLEVEL 5
+#define PATCHLEVEL 6
 
 #endif /* _PATCHLEVEL_H_ */

subst.c

@@ -6412,6 +6412,13 @@ command_substitute (string, quoted, flags)
       /* The currently executing shell is not interactive. */
       interactive = 0;
 
+#if defined (JOB_CONTROL)
+      /* Invariant: in child processes started to run command substitutions,
+	 pipeline_pgrp == shell_pgrp. Other parts of the shell assume this. */
+      if (pipeline_pgrp > 0 && pipeline_pgrp != shell_pgrp)
+	shell_pgrp = pipeline_pgrp;
+#endif
+
       set_sigint_handler ();	/* XXX */
 
       free_pushed_string_input ();