Update name in screenshot markers (#63)

The iBooks Store was renamed several years ago -- the comment markers
should follow the current name.

When we're able to publish an ePUB version again[1], we probably want to
retake all of the screenshots. We can update the value of COMMIT in
the script at that time, to help us after that so we can find and retake
only things that change.

Fixes rdar://101972172

1: #2

Author: amartini51

Sources/TSPL/TSPL.docc/GuidedTour/GuidedTour.md

@@ -263,9 +263,7 @@ occupations["Jayne"] = "Public Relations"
   ```
 -->
 
-<!--
-  iBooks Store screenshot begins here.
--->
+<!-- Apple Books screenshot begins here. -->
 
 Arrays automatically grow as you add elements.
 
@@ -390,9 +388,7 @@ or contains `nil` to indicate that a value is missing.
 Write a question mark (`?`) after the type of a value
 to mark the value as optional.
 
-<!--
-  iBooks Store screenshot ends here.
--->
+<!-- Apple Books screenshot ends here. -->
 
 <!--
   REFERENCE

Sources/TSPL/TSPL.docc/LanguageGuide/AdvancedOperators.md

@@ -72,9 +72,7 @@ which has its first four bits set to `0`,
 and its second four bits set to `1`.
 This is equivalent to a decimal value of `15`.
 
-<!--
-  iBooks Store screenshot begins here.
--->
+<!-- Apple Books screenshot begins here. -->
 
 The bitwise NOT operator is then used to create a new constant called `invertedBits`,
 which is equal to `initialBits`,
@@ -122,9 +120,7 @@ if the bits are equal to `1` in *either* input number:
 
 ![](bitwiseOR)
 
-<!--
-  iBooks Store screenshot ends here.
--->
+<!-- Apple Books screenshot ends here. -->
 
 In the example below,
 the values of `someBits` and `moreBits` have different bits set to `1`.

Sources/TSPL/TSPL.docc/LanguageGuide/ControlFlow.md

@@ -308,9 +308,7 @@ while <#condition#> {
 This example plays a simple game of *Snakes and Ladders*
 (also known as *Chutes and Ladders*):
 
-<!--
-  iBooks Store screenshot begins here.
--->
+<!-- Apple Books screenshot begins here. -->
 
 ![](snakesAndLadders)
 
@@ -364,9 +362,7 @@ board[14] = -10; board[19] = -11; board[22] = -02; board[24] = -08
   ```
 -->
 
-<!--
-  iBooks Store screenshot ends here.
--->
+<!-- Apple Books screenshot ends here. -->
 
 Square 3 contains the bottom of a ladder that moves you up to square 11.
 To represent this, `board[03]` is equal to `+08`,

Sources/TSPL/TSPL.docc/LanguageGuide/Properties.md

@@ -431,9 +431,7 @@ Setting the `center` property calls the setter for `center`,
 which modifies the `x` and `y` values of the stored `origin` property,
 and moves the square to its new position.
 
-<!--
-  iBooks Store screenshot begins here.
--->
+<!-- Apple Books screenshot begins here. -->
 
 ![](computedProperties)
 
@@ -484,9 +482,7 @@ struct AlternativeRect {
   ```
 -->
 
-<!--
-  iBooks Store screenshot ends here.
--->
+<!-- Apple Books screenshot ends here. -->
 
 ### Shorthand Getter Declaration
 

Sources/TSPL/TSPL.docc/ReferenceManual/Expressions.md

@@ -875,9 +875,7 @@ struct Point {
   ```
 -->
 
-<!--
-  iBooks Store screenshot begins here.
--->
+<!-- Apple Books screenshot begins here. -->
 
 > Grammar of a self expression:
 >
@@ -960,9 +958,7 @@ it's understood to be asynchronous.
 There are several special forms
 that allow closures to be written more concisely:
 
-<!--
-  iBooks Store screenshot ends here.
--->
+<!-- Apple Books screenshot ends here. -->
 
 - A closure can omit the types
   of its parameters, its return type, or both.

bin/find_screenshot_changes

@@ -0,0 +1,41 @@
+#! /usr/bin/env zsh
+
+setopt ERR_EXIT NO_UNSET PIPE_FAIL
+
+# This script helps identify changes that show up in screenshots.
+#
+# Set $COMMIT to the oldest commit this script should consider:
+# ideally, that's the commit when the current screenshots were taken.
+#
+# Lines in the output that start with whitespace are unchanged since $COMMIT.
+# Lines that start with a commit ID were changed in that commit, after $COMMIT.
+#
+# To check whether we need to re-shoot the screenshots,
+# run this script and check whether any lines start with commit IDs.
+# For example:
+#
+#     ./bin/find_screenshot_changes.zsh | grep -v '^ '
+#
+# To show those commits that made scheenshot changes:
+#
+#     ./bin/find_screenshot_changes.zsh |
+#     cut -d ' ' -f 1 |
+#     sort -u |
+#     xargs -L1 git --no-pager log -1
+
+BEGIN='<!-- Apple Books screenshot begins here -->'
+END='<!-- Apple Books screenshot ends here -->'
+
+# The commit when these comment markers were originally added.
+# COMMIT=64627a260ed600015dbad1a853d8b85f611b61d4
+
+# The commit when the content was converted from RST to markdown.
+COMMIT=96f0925407c6bd9eadd9d58d253bad3e1ef7a9f2
+
+cd Sources/TSPL/TSPL.docc
+git grep --files-with-matches $BEGIN | while IFS= read -r FILE
+do
+    git --no-pager blame -bs $COMMIT.. -L /$BEGIN/,/$END/ $FILE
+    echo
+    echo
+done