[DOC] Enhanced RDoc for String (#5730)

Treats:

    #start_with?
    #end_with?
    #delete_prefix
    #delete_prefix!
    #delete_suffix
    #delete_suffix!

doc/string/delete_prefix.rdoc

@@ -0,0 +1,8 @@
+Returns a copy of +self+ with leading substring <tt>prefix</tt> removed:
+
+  'hello'.delete_prefix('hel')      # => "lo"
+  'hello'.delete_prefix('llo')      # => "hello"
+  'тест'.delete_prefix('те')        # => "ст"
+  'こんにちは'.delete_prefix('こん')  # => "にちは"
+
+Related: String#delete_prefix!, String#delete_suffix.

doc/string/delete_suffix.rdoc

@@ -0,0 +1,8 @@
+Returns a copy of +self+ with trailing substring <tt>suffix</tt> removed:
+
+  'hello'.delete_suffix('llo')      # => "he"
+  'hello'.delete_suffix('hel')      # => "hello"
+  'тест'.delete_suffix('ст')        # => "те"
+  'こんにちは'.delete_suffix('ちは')  # => "こんに"
+
+Related: String#delete_suffix!, String#delete_prefix.

doc/string/end_with_p.rdoc

@@ -0,0 +1,11 @@
+Returns whether +self+ ends with any of the given +strings+.
+
+Returns +true+ if any given string matches the end, +false+ otherwise:
+
+  'hello'.end_with?('ello')               #=> true
+  'hello'.end_with?('heaven', 'ello')     #=> true
+  'hello'.end_with?('heaven', 'paradise') #=> false
+  'тест'.end_with?('т')                   # => true
+  'こんにちは'.end_with?('は')              # => true
+
+Related: String#start_with?.

doc/string/start_with_p.rdoc

@@ -0,0 +1,18 @@
+Returns whether +self+ starts with any of the given +string_or_regexp+.
+
+Matches patterns against the beginning of+self+.
+For each given +string_or_regexp+, the pattern is:
+
+- +string_or_regexp+ itself, if it is a Regexp.
+- <tt>Regexp.quote(string_or_regexp)</tt>, if +string_or_regexp+ is a string.
+
+Returns +true+ if any pattern matches the beginning, +false+ otherwise:
+
+  'hello'.start_with?('hell')               # => true
+  'hello'.start_with?(/H/i)                 # => true
+  'hello'.start_with?('heaven', 'hell')     # => true
+  'hello'.start_with?('heaven', 'paradise') # => false
+  'тест'.start_with?('т')                   # => true
+  'こんにちは'.start_with?('こ')              # => true
+
+Related: String#end_with?.

string.c

@@ -10510,17 +10510,10 @@ rb_str_rpartition(VALUE str, VALUE sep)
 
 /*
  *  call-seq:
- *     str.start_with?([prefixes]+)   -> true or false
+ *    start_with?(*string_or_regexp) -> true or false
  *
- *  Returns true if +str+ starts with one of the +prefixes+ given.
- *  Each of the +prefixes+ should be a String or a Regexp.
+ *  :include: doc/string/start_with_p.rdoc
  *
- *    "hello".start_with?("hell")               #=> true
- *    "hello".start_with?(/H/i)                 #=> true
- *
- *    # returns true if one of the prefixes matches.
- *    "hello".start_with?("heaven", "hell")     #=> true
- *    "hello".start_with?("heaven", "paradise") #=> false
  */
 
 static VALUE
@@ -10547,15 +10540,10 @@ rb_str_start_with(int argc, VALUE *argv, VALUE str)
 
 /*
  *  call-seq:
- *     str.end_with?([suffixes]+)   -> true or false
+ *    end_with?(*strings) -> true or false
  *
- *  Returns true if +str+ ends with one of the +suffixes+ given.
+ *  :include: doc/string/end_with_p.rdoc
  *
- *    "hello".end_with?("ello")               #=> true
- *
- *    # returns true if one of the +suffixes+ matches.
- *    "hello".end_with?("heaven", "ello")     #=> true
- *    "hello".end_with?("heaven", "paradise") #=> false
  */
 
 static VALUE
@@ -10616,13 +10604,11 @@ deleted_prefix_length(VALUE str, VALUE prefix)
 
 /*
  *  call-seq:
- *     str.delete_prefix!(prefix) -> self or nil
+ *    delete_prefix!(prefix) -> self or nil
  *
- *  Deletes leading <code>prefix</code> from <i>str</i>, returning
- *  <code>nil</code> if no change was made.
+ *  Like String#delete_prefix, except that +self+ is modified in place.
+ *  Returns +self+ if the prefix is removed, +nil+ otherwise.
  *
- *     "hello".delete_prefix!("hel") #=> "lo"
- *     "hello".delete_prefix!("llo") #=> nil
  */
 
 static VALUE
@@ -10639,12 +10625,10 @@ rb_str_delete_prefix_bang(VALUE str, VALUE prefix)
 
 /*
  *  call-seq:
- *     str.delete_prefix(prefix) -> new_str
+ *    delete_prefix(prefix) -> new_string
  *
- *  Returns a copy of <i>str</i> with leading <code>prefix</code> deleted.
+ *  :include: doc/string/delete_prefix.rdoc
  *
- *     "hello".delete_prefix("hel") #=> "lo"
- *     "hello".delete_prefix("llo") #=> "hello"
  */
 
 static VALUE
@@ -10694,13 +10678,11 @@ deleted_suffix_length(VALUE str, VALUE suffix)
 
 /*
  *  call-seq:
- *     str.delete_suffix!(suffix) -> self or nil
+ *    delete_suffix!(suffix) -> self or nil
  *
- *  Deletes trailing <code>suffix</code> from <i>str</i>, returning
- *  <code>nil</code> if no change was made.
+ *  Like String#delete_suffix, except that +self+ is modified in place.
+ *  Returns +self+ if the suffix is removed, +nil+ otherwise.
  *
- *     "hello".delete_suffix!("llo") #=> "he"
- *     "hello".delete_suffix!("hel") #=> nil
  */
 
 static VALUE
@@ -10725,12 +10707,10 @@ rb_str_delete_suffix_bang(VALUE str, VALUE suffix)
 
 /*
  *  call-seq:
- *     str.delete_suffix(suffix) -> new_str
+ *     str.delete_suffix(suffix) -> new_string
  *
- *  Returns a copy of <i>str</i> with trailing <code>suffix</code> deleted.
+ *  :include: doc/string/delete_suffix.rdoc
  *
- *     "hello".delete_suffix("llo") #=> "he"
- *     "hello".delete_suffix("hel") #=> "hello"
  */
 
 static VALUE