Job control in ASH is broken.

Test script:
# sleep 20 &
# jobs %sle

Expected output:
# sleep 20 &
# jobs %sle
[1] + Running      sleep 20
# _

Actual Output:
# sleep 20 &
# jobs %sle
-sh: jobs: %sle: ambiguous
# _

Cause:
in busybox/shell/ash.c:getjob:

        found = 0;
        while (1) {
                if (!jp)
                        goto err;
                if (match(jp->ps[0].cmd, p)) {
                        if (found)
                                goto err;
                        found = jp;
                        err_msg = "%s: ambiguous";
                }
                jp = jp->prev_job;
        }

Fix:
The above code can NEVER work, because there is no exit from the while loop even if the correct job is found.  It should be replaced with this:

        found = 0;
        while (jp) {
                if (match(jp->ps[0].cmd, p)) {
                        if (found)
                                goto err;
                        found = jp;
                        err_msg = "%s: ambiguous";
                }
                jp = jp->prev_job;
        }
        if (!found)
                goto err;

Note that it appears err_msg isn't set before going to err, but it is set at the start of the function.

I'm not a regular around here, so I'll leave this here for someone with commit access to make this change.