Correct reordering of jobs in job_promote

job_promote attempts to bring the most recently "touched" job to the front
of the job list. It did this via:

    std::rotate(begin, job, end)

However this has the effect of pushing job-1 to the end. That is,
promoting '2' in [1, 2, 3] would result in [2, 3, 1].

Correct this by replacing it with:

    std::rotate(begin, job, job+1);

now we get the desired [2, 1, 3].

Also add a test.

src/parser.cpp

@@ -571,7 +571,7 @@ void parser_t::job_promote(job_t *job) {
     assert(loc != job_list.end());
 
     // Move the job to the beginning.
-    std::rotate(job_list.begin(), loc, job_list.end());
+    std::rotate(job_list.begin(), loc, std::next(loc));
 }
 
 job_t *parser_t::job_get(job_id_t id) {

tests/checks/job_ids.fish

@@ -0,0 +1,37 @@
+# RUN: %fish %s
+
+# Ensure that job IDs are sequential.
+
+status job-control full
+
+set -g tokill
+
+function func100
+    sleep 100 &
+    set -g tokill $tokill $last_pid
+end
+
+function func200
+    sleep 200 &
+    set -g tokill $tokill $last_pid
+end
+
+
+func100
+func200
+
+sleep 300 &
+set -g tokill $tokill $last_pid
+
+jobs
+
+#CHECK: Job	Group	CPU	State	Command
+#CHECK: 3{{.*\t}}sleep 300 &
+#CHECK: 2{{.*\t}}sleep 200 &
+#CHECK: 1{{.*\t}}sleep 100 &
+
+status job-control interactive
+
+for pid in $tokill
+    command kill -9 $pid
+end