Remove "Large Changes" documentation and make some minor behavioral improvements

Summary:
Depends on D19296. Ref T13110.

  - Remove the "Large Changesets" documentation since we now degrade very large changesets and I don't have any evidence that anyone has ever tried to follow any of the recommendations in this document.
  - Remove references to it.
  - When an older revision doesn't have denormalized size information on the Revision object itself, don't render a scale element (instead of rendering a bogus one).
  - Try to improve terminology consistency around "Large Change" (100-1000 files) vs "Very Large Change" (1000+ files) vs "Enormous Change" (too large to hold in memory).

Test Plan: Viewed revisions; grepped for documentation.

Maniphest Tasks: T13110

Differential Revision: https://secure.phabricator.com/D19298

src/applications/differential/conduit/DifferentialCreateRawDiffConduitAPIMethod.php

@@ -56,10 +56,7 @@ final class DifferentialCreateRawDiffConduitAPIMethod
       throw new Exception(
         pht(
           'The raw diff you have submitted is too large to parse (it affects '.
-          'more than %s paths and hunks). Differential should only be used '.
-          'for changes which are small enough to receive detailed human '.
-          'review. See "Differential User Guide: Large Changes" in the '.
-          'documentation for more information.',
+          'more than %s paths and hunks).',
           new PhutilNumber($raw_limit)));
     }
 

src/applications/differential/controller/DifferentialRevisionViewController.php

@@ -158,7 +158,7 @@ final class DifferentialRevisionViewController extends DifferentialController {
     if (count($changesets) > $limit && !$large) {
       $count = count($changesets);
       $warning = new PHUIInfoView();
-      $warning->setTitle(pht('Very Large Diff'));
+      $warning->setTitle(pht('Large Diff'));
       $warning->setSeverity(PHUIInfoView::SEVERITY_WARNING);
       $warning->appendChild(hsprintf(
         '%s <strong>%s</strong>',

src/applications/differential/storage/DifferentialRevision.php

@@ -742,6 +742,12 @@ final class DifferentialRevision extends DifferentialDAO
     return $this->getProperty(self::PROPERTY_LINES_REMOVED);
   }
 
+  public function hasLineCounts() {
+    // This data was not populated on older revisions, so it may not be
+    // present on all revisions.
+    return isset($this->properties[self::PROPERTY_LINES_ADDED]);
+  }
+
   public function getRevisionScaleGlyphs() {
     $add = $this->getAddedLineCount();
     $rem = $this->getRemovedLineCount();

src/applications/differential/view/DifferentialRevisionListView.php

@@ -109,7 +109,10 @@ final class DifferentialRevisionListView extends AphrontView {
       $item->setHeader($revision->getTitle());
       $item->setHref($revision->getURI());
 
-      $item->addAttribute($this->renderRevisionSize($revision));
+      $size = $this->renderRevisionSize($revision);
+      if ($size !== null) {
+        $item->addAttribute($size);
+      }
 
       if ($revision->getHasDraft($viewer)) {
         $draft = id(new PHUIIconView())
@@ -193,6 +196,10 @@ final class DifferentialRevisionListView extends AphrontView {
   }
 
   private function renderRevisionSize(DifferentialRevision $revision) {
+    if (!$revision->hasLineCounts()) {
+      return null;
+    }
+
     $size = array();
 
     $glyphs = $revision->getRevisionScaleGlyphs();

src/docs/flavor/writing_reviewable_code.diviner

@@ -74,9 +74,6 @@ often well-correlated with complexity.
 We generally follow these practices in Phabricator. The median change size for
 Phabricator is 35 lines.
 
-See @{article:Differential User Guide: Large Changes} for information about
-reviewing big checkins.
-
 = Write Sensible Commit Messages =
 
 There are lots of resources for this on the internet. All of them say pretty

src/docs/user/userguide/differential.diviner

@@ -66,8 +66,6 @@ Continue by:
   - diving into the details of inline comments in
     @{article:Differential User Guide: Inline Comments}; or
   - reading the FAQ at @{article:Differential User Guide: FAQ}; or
-  - learning about handling large changesets in
-    @{article:Differential User Guide: Large Changes}; or
   - learning about test plans in
     @{article:Differential User Guide: Test Plans}; or
   - learning more about Herald in @{article:Herald User Guide}.

src/docs/user/userguide/differential_large_changes.diviner

@@ -1,54 +0,0 @@
-@title Differential User Guide: Large Changes
-@group userguide
-
-Dealing with huge changesets, and when **not** to use Differential.
-
-= Overview =
-
-When you want code review for a given changeset, Differential is not always the
-right tool to use. The rule of thumb is that you should only send changes to
-Differential if you expect humans to review the actual differences in the source
-code from the web interface. This should cover the vast majority of changes but,
-for example, you usually should //not// submit changes like these through
-Differential:
-
-  - Committing an entire open source project to a private repo somewhere so
-    you can fork it or link against it.
-  - Committing an enormous text datafile, like a list of every English word or a
-    dump of a database.
-  - Making a trivial (e.g., find/replace or codemod) edit to 10,000 files.
-
-You can still try submitting these kinds of changes, but you may encounter
-problems getting them to work (database or connection timeouts, for example).
-Differential is pretty fast and scalable, but at some point either it or the
-browser will break down: you simply can't show nine million files on a webpage.
-
-More importantly, in all these cases, the text of the changes won't be reviewed
-by a human. The metadata associated with the change is what needs review (e.g.,
-what are you checking in, where are you putting it, and why? Does the change
-make sense? In the case of automated transformations, what script did you use?).
-To get review for these types of changes, one of these strategies will usually
-work better than trying to get the entire change into Differential:
-
-  - Send an email/AIM/IRC to your reviewer(s) like "Hey, I'm going to check in
-    the source for MySQL 9.3.1 to /full/path/to/whatever. The change is staged
-    in /home/whatever/path/somewhere if you want to take a look. Can I put your
-    name on the review?". This is best for straightforward changes. The reviewer
-    is not going to review MySQL's source itself, instead they are reviewing the
-    change metadata: which version are you checking in, why are you checking it
-    in, and where are you putting it? You won't be able to use "arc commit" or
-    "arc amend" to actually push the change. Just use "svn" or "git" and
-    manually edit the commit message instead. (It is normally sufficient to add
-    a "Reviewed By: <username>" field.)
-  - Create a Differential revision with only the metadata, like the script you
-    used to make automated changes or a text file explaining what you're doing,
-    and maybe a sample of some of the changes if they were automated. Include a
-    link to where the changes are staged so reviewers can look at the actual
-    changeset if they want to. This is best for more complicated changes, since
-    Differential can still be used for discussion and provide a permanent record
-    others can refer to. Once the revision is accepted, amend your local commit
-    (e.g. by `git commit --amend`) with the real change and push as usual.
-
-These kinds of changes are generally rare and don't have much in common, which
-is why there's no explicit support for them in Differential. If you frequently
-run into cases which Differential doesn't handle, let us know what they are.