scripts: Added -c/--compare for comparing specific result rows

Example:

  $ ./scripts/csv.py lfs.code.csv \
          -bfunction -fsize \
          -clfsr_rbyd_appendrattr
  function                                size
  lfsr_rbyd_appendrattr                   3598
  lfsr_mdir_commit                        5176 (+43.9%)
  lfsr_btree_commit__.constprop.0         3955 (+9.9%)
  lfsr_file_flush_                        2729 (-24.2%)
  lfsr_file_carve                         2503 (-30.4%)
  lfsr_mountinited                        2357 (-34.5%)
  ... snip ...

I don't think this is immediately useful for our code/stack/etc
measurement scripts, but it's certainly useful in csv.py for comparing
results at a high level.

And by useful I mean it replaces a 40-line long awk script that has
outgrown its original purpose...

scripts/stack.py

@@ -340,6 +340,7 @@ def table(Result, results, diff_results=None, *,
         summary=False,
         all=False,
         percent=False,
+        compare=None,
         depth=None,
         hot=None,
         **_):
@@ -401,8 +402,22 @@ def table(Result, results, diff_results=None, *,
                         getattr(diff_table.get(name), k, None))
                     for k in fields)]
 
+    # find compare entry if there is one
+    if compare is not None:
+        compare_result = table.get(','.join(str(k) for k in compare))
+
     # sort again, now with diff info, note that python's sort is stable
     names.sort()
+    if compare is not None:
+        names.sort(
+                key=lambda n: (
+                    table.get(n) == compare_result,
+                    tuple(
+                        types[k].ratio(
+                                getattr(table.get(n), k, None),
+                                getattr(compare_result, k, None))
+                            for k in fields)),
+                reverse=True)
     if diff_results is not None:
         names.sort(
                 key=lambda n: tuple(
@@ -454,14 +469,30 @@ def table(Result, results, diff_results=None, *,
     # entry helper
     def table_entry(name, r, diff_r=None):
         entry = [name]
-        if diff_results is None:
+        # normal entry?
+        if ((compare is None or r == compare_result)
+                and diff_results is None):
             for k in fields:
                 entry.append(
                         (getattr(r, k).table(),
                                 getattr(getattr(r, k), 'notes', lambda: [])())
                             if getattr(r, k, None) is not None
                             else types[k].none)
-        elif percent:
+        # compare entry?
+        elif compare is not None and diff_results is None:
+            for k in fields:
+                entry.append(
+                        (getattr(r, k).table()
+                                if getattr(r, k, None) is not None
+                                else types[k].none,
+                            (lambda t: ['+∞%'] if t == +mt.inf
+                                    else ['-∞%'] if t == -mt.inf
+                                    else ['%+.1f%%' % (100*t)])(
+                                types[k].ratio(
+                                    getattr(r, k, None),
+                                    getattr(compare_result, k, None)))))
+        # percent entry?
+        elif diff_results is not None and percent:
             for k in fields:
                 entry.append(
                         (getattr(r, k).table()
@@ -473,7 +504,8 @@ def table(Result, results, diff_results=None, *,
                                 types[k].ratio(
                                     getattr(r, k, None),
                                     getattr(diff_r, k, None)))))
-        else:
+        # diff entry?
+        elif diff_results is not None:
             for k in fields:
                 entry.append(getattr(diff_r, k).table()
                         if getattr(diff_r, k, None) is not None
@@ -569,13 +601,14 @@ def table(Result, results, diff_results=None, *,
                          "|   ",
                          "    "))
 
-    # total
-    r = next(iter(fold(Result, results, by=[])), None)
-    if diff_results is None:
-        diff_r = None
-    else:
-        diff_r = next(iter(fold(Result, diff_results, by=[])), None)
-    lines.append(table_entry('TOTAL', r, diff_r))
+    # total, unless we're comparing
+    if summary or not (compare is not None and diff_results is None):
+        r = next(iter(fold(Result, results, by=[])), None)
+        if diff_results is None:
+            diff_r = None
+        else:
+            diff_r = next(iter(fold(Result, diff_results, by=[])), None)
+        lines.append(table_entry('TOTAL', r, diff_r))
 
     # homogenize
     lines = [
@@ -745,6 +778,10 @@ if __name__ == "__main__":
             '-p', '--percent',
             action='store_true',
             help="Only show percentage change, not a full diff.")
+    parser.add_argument(
+            '-c', '--compare',
+            type=lambda x: tuple(v.strip() for v in x.split(',')),
+            help="Compare results to the row matching this by pattern.")
     parser.add_argument(
             '-b', '--by',
             action='append',