Merge branch 'jk/revision-walk-stop-at-max-count'

"git log -n 1 -- rarely-touched-path" was spending unnecessary
cycles after showing the first change to find the next one, only to
discard it.

* jk/revision-walk-stop-at-max-count:
revision: avoid work after --max-count is reached

diff --combined revision.c
index c64bf68fa1f84a226cec97ddaf1970cf0aaa308b,7e3965557ac2e2d2d432e47b8b745c4dc0e184b6..9e8f47a25d8def94cbf2a8389039e4d3d670cd06
--- 1/revision.c
--- 2/revision.c
+++ b/revision.c
@@@ -1000,7 -1000,7 +1000,7 @@@ static int add_parents_only(struct rev_
                flags ^= UNINTERESTING;
                arg++;
        }
 -      if (get_sha1(arg, sha1))
 +      if (get_sha1_committish(arg, sha1))
                return 0;
        while (1) {
                it = get_reference(revs, arg, sha1, 0);
@@@ -1114,16 -1114,16 +1114,16 @@@ static void prepare_show_merge(struct r
        revs->limited = 1;
  }
  
 -int handle_revision_arg(const char *arg_, struct rev_info *revs,
 -                      int flags,
 -                      int cant_be_filename)
 +int handle_revision_arg(const char *arg_, struct rev_info *revs, int flags, unsigned revarg_opt)
  {
 -      unsigned mode;
 +      struct object_context oc;
        char *dotdot;
        struct object *object;
        unsigned char sha1[20];
        int local_flags;
        const char *arg = arg_;
 +      int cant_be_filename = revarg_opt & REVARG_CANNOT_BE_FILENAME;
 +      unsigned get_sha1_flags = 0;
  
        dotdot = strstr(arg, "..");
        if (dotdot) {
@@@ -1141,8 -1141,8 +1141,8 @@@
                        next = "HEAD";
                if (dotdot == arg)
                        this = "HEAD";
 -              if (!get_sha1(this, from_sha1) &&
 -                  !get_sha1(next, sha1)) {
 +              if (!get_sha1_committish(this, from_sha1) &&
 +                  !get_sha1_committish(next, sha1)) {
                        struct commit *a, *b;
                        struct commit_list *exclude;
  
@@@ -1201,17 -1201,13 +1201,17 @@@
                local_flags = UNINTERESTING;
                arg++;
        }
 -      if (get_sha1_with_mode(arg, sha1, &mode))
 +
 +      if (revarg_opt & REVARG_COMMITTISH)
 +              get_sha1_flags = GET_SHA1_COMMITTISH;
 +
 +      if (get_sha1_with_context(arg, get_sha1_flags, sha1, &oc))
                return revs->ignore_missing ? 0 : -1;
        if (!cant_be_filename)
                verify_non_filename(revs->prefix, arg);
        object = get_reference(revs, arg, sha1, flags ^ local_flags);
        add_rev_cmdline(revs, object, arg_, REV_CMD_REV, flags ^ local_flags);
 -      add_pending_object_with_mode(revs, object, arg, mode);
 +      add_pending_object_with_mode(revs, object, arg, oc.mode);
        return 0;
  }
  
@@@ -1261,7 -1257,7 +1261,7 @@@ static void read_revisions_from_stdin(s
                        }
                        die("options not supported in --stdin mode");
                }
 -              if (handle_revision_arg(sb.buf, revs, 0, 1))
 +              if (handle_revision_arg(sb.buf, revs, 0, REVARG_CANNOT_BE_FILENAME))
                        die("bad revision '%s'", sb.buf);
        }
        if (seen_dashdash)
@@@ -1712,7 -1708,7 +1712,7 @@@ static int handle_revision_pseudo_opt(c
   */
  int setup_revisions(int argc, const char **argv, struct rev_info *revs, struct setup_revision_opt *opt)
  {
 -      int i, flags, left, seen_dashdash, read_from_stdin, got_rev_arg = 0;
 +      int i, flags, left, seen_dashdash, read_from_stdin, got_rev_arg = 0, revarg_opt;
        struct cmdline_pathspec prune_data;
        const char *submodule = NULL;
  
@@@ -1740,9 -1736,6 +1740,9 @@@
  
        /* Second, deal with arguments and options */
        flags = 0;
 +      revarg_opt = opt ? opt->revarg_opt : 0;
 +      if (seen_dashdash)
 +              revarg_opt |= REVARG_CANNOT_BE_FILENAME;
        read_from_stdin = 0;
        for (left = i = 1; i < argc; i++) {
                const char *arg = argv[i];
@@@ -1778,8 -1771,7 +1778,8 @@@
                        continue;
                }
  
 -              if (handle_revision_arg(arg, revs, flags, seen_dashdash)) {
 +
 +              if (handle_revision_arg(arg, revs, flags, revarg_opt)) {
                        int j;
                        if (seen_dashdash || *arg == '^')
                                die("bad revision '%s'", arg);
@@@ -1830,11 -1822,11 +1830,11 @@@
        if (revs->def && !revs->pending.nr && !got_rev_arg) {
                unsigned char sha1[20];
                struct object *object;
 -              unsigned mode;
 -              if (get_sha1_with_mode(revs->def, sha1, &mode))
 +              struct object_context oc;
 +              if (get_sha1_with_context(revs->def, 0, sha1, &oc))
                        die("bad default revision '%s'", revs->def);
                object = get_reference(revs, revs->def, sha1, 0);
 -              add_pending_object_with_mode(revs, object, revs->def, mode);
 +              add_pending_object_with_mode(revs, object, revs->def, oc.mode);
        }
  
        /* Did the user ask for any diff output? Run the diff! */
@@@ -2369,29 -2361,28 +2369,28 @@@ static struct commit *get_revision_inte
        }
  
        /*
-        * Now pick up what they want to give us
+        * If our max_count counter has reached zero, then we are done. We
+        * don't simply return NULL because we still might need to show
+        * boundary commits. But we want to avoid calling get_revision_1, which
+        * might do a considerable amount of work finding the next commit only
+        * for us to throw it away.
+        *
+        * If it is non-zero, then either we don't have a max_count at all
+        * (-1), or it is still counting, in which case we decrement.
         */
-       c = get_revision_1(revs);
-       if (c) {
-               while (0 < revs->skip_count) {
-                       revs->skip_count--;
-                       c = get_revision_1(revs);
-                       if (!c)
-                               break;
+       if (revs->max_count) {
+               c = get_revision_1(revs);
+               if (c) {
+                       while (0 < revs->skip_count) {
+                               revs->skip_count--;
+                               c = get_revision_1(revs);
+                               if (!c)
+                                       break;
+                       }
                }
-       }
  
-       /*
-        * Check the max_count.
-        */
-       switch (revs->max_count) {
-       case -1:
-               break;
-       case 0:
-               c = NULL;
-               break;
-       default:
-               revs->max_count--;
+               if (revs->max_count > 0)
+                       revs->max_count--;
        }
  
        if (c)