Page#dir: ensure it ends in a slash

[parkr]

Fixes #3974.

/cc @envygeeks, because I'm sure you have a faster/more elegant/more performant solution for this problem.
/cc @jekyll/core for review!

[envygeeks]

def _new(url)
  return url if url.end_with?("/") || url == "/"

  url = File.dirname(url)
  url == "/" ? url : "#{url}/"
end

Calculating -------------------------------------
              _old:/    60.796k i/100ms
              _new:/    72.437k i/100ms
-------------------------------------------------
              _old:/      2.489M (± 4.8%) i/s -     12.463M
              _new:/      4.657M (± 8.5%) i/s -     23.107M

Comparison:
              _new:/:  4657430.1 i/s
              _old:/:  2489307.2 i/s - 1.87x slower

Calculating -------------------------------------
   _old:/hello/world    43.174k i/100ms
   _new:/hello/world    46.844k i/100ms
-------------------------------------------------
   _old:/hello/world      1.172M (± 3.5%) i/s -      5.872M
   _new:/hello/world      1.261M (± 4.0%) i/s -      6.324M

Comparison:
   _new:/hello/world:  1261134.4 i/s
   _old:/hello/world:  1172086.2 i/s - 1.08x slower

Calculating -------------------------------------
  _old:/hello/world/    61.655k i/100ms
  _new:/hello/world/    72.840k i/100ms
-------------------------------------------------
  _old:/hello/world/      2.531M (± 3.4%) i/s -     12.639M
  _new:/hello/world/      4.752M (± 4.0%) i/s -     23.746M

Comparison:
  _new:/hello/world/:  4751972.9 i/s
  _old:/hello/world/:  2531102.8 i/s - 1.88x slower

---

You can edge out more performance with url + "/" but that's a violation of Github's styleguide which I follow so I did not include it in the results.

[alfredxing]

👍 for @envygeeks' function. Though I think the || url == "/" can be removed from the first line? (Since .end_with? "/" should return true in this case)

[envygeeks]

@alfredxing it could be, but it's slower.

[alfredxing]

OK! But (just a sanity check) doesn't the first part (url.end_with?("/")) get evaluated first, then url == "/"?

[envygeeks]

It should but sadly the code ran faster with a more direct check, in there too. I'll double check the benches again just to make sure, because you should and probably are right.

[parkr]

Ok, I just pushed up another iteration. A bit longer, but doing every little thing helped:

Calculating -------------------------------------
            pre_pr:/   151.086k i/100ms
                pr:/   168.945k i/100ms
         envygeeks:/   168.146k i/100ms
-------------------------------------------------
            pre_pr:/      5.652M (± 4.5%) i/s -     28.253M
                pr:/      8.017M (± 5.4%) i/s -     40.040M
         envygeeks:/      7.445M (±10.1%) i/s -     36.824M

Comparison:
                pr:/:  8017279.2 i/s
         envygeeks:/:  7444605.1 i/s - 1.08x slower
            pre_pr:/:  5651646.7 i/s - 1.42x slower

Calculating -------------------------------------
pre_pr:/some/very/very/long/path/to/a/file/i/like
                        87.137k i/100ms
pr:/some/very/very/long/path/to/a/file/i/like
                        62.901k i/100ms
envygeeks:/some/very/very/long/path/to/a/file/i/like
                        60.416k i/100ms
-------------------------------------------------
pre_pr:/some/very/very/long/path/to/a/file/i/like
                          1.396M (± 6.4%) i/s -      6.971M
pr:/some/very/very/long/path/to/a/file/i/like
                        895.033k (± 5.4%) i/s -      4.466M
envygeeks:/some/very/very/long/path/to/a/file/i/like
                        891.898k (± 4.9%) i/s -      4.471M

Comparison:
pre_pr:/some/very/very/long/path/to/a/file/i/like:  1396111.2 i/s
pr:/some/very/very/long/path/to/a/file/i/like:   895033.2 i/s - 1.56x slower
envygeeks:/some/very/very/long/path/to/a/file/i/like:   891897.8 i/s - 1.57x slower

Calculating -------------------------------------
pre_pr:/some/very/very/long/path/to/a/file/i/like/
                       150.546k i/100ms
pr:/some/very/very/long/path/to/a/file/i/like/
                       165.396k i/100ms
envygeeks:/some/very/very/long/path/to/a/file/i/like/
                       162.486k i/100ms
-------------------------------------------------
pre_pr:/some/very/very/long/path/to/a/file/i/like/
                          5.570M (± 5.8%) i/s -     27.851M
pr:/some/very/very/long/path/to/a/file/i/like/
                          7.821M (± 7.1%) i/s -     39.033M
envygeeks:/some/very/very/long/path/to/a/file/i/like/
                          7.734M (± 7.6%) i/s -     38.509M

Comparison:
pr:/some/very/very/long/path/to/a/file/i/like/:  7821419.0 i/s
envygeeks:/some/very/very/long/path/to/a/file/i/like/:  7733559.1 i/s - 1.01x slower
pre_pr:/some/very/very/long/path/to/a/file/i/like/:  5569945.8 i/s - 1.40x slower

[parkr]

@jekyllbot: merge +bug