Pull Regexp syntax out of Death test section in advanced.md

Regexps seem to have nothing in common with death tests, yet their description is planted right in the middle of the death test section.

This CL pulls the regexp section one level up and just before death tests.

PiperOrigin-RevId: 721817710
Change-Id: Idc52f450fb10960a590ceb1a70339f86d4478fe4

Author: Abseil Team

docs/advanced.md

@@ -405,6 +405,51 @@ EXPECT_TRUE(IsCorrectPointIntVector(point_ints))
 For more details regarding `AbslStringify()` and its integration with other
 libraries, see go/abslstringify.
 
+## Regular Expression Syntax
+
+When built with Bazel and using Abseil, GoogleTest uses the
+[RE2](https://github.com/google/re2/wiki/Syntax) syntax. Otherwise, for POSIX
+systems (Linux, Cygwin, Mac), GoogleTest uses the
+[POSIX extended regular expression](https://pubs.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap09.html#tag_09_04)
+syntax. To learn about POSIX syntax, you may want to read this
+[Wikipedia entry](https://en.wikipedia.org/wiki/Regular_expression#POSIX_extended).
+
+On Windows, GoogleTest uses its own simple regular expression implementation. It
+lacks many features. For example, we don't support union (`"x|y"`), grouping
+(`"(xy)"`), brackets (`"[xy]"`), and repetition count (`"x{5,7}"`), among
+others. Below is what we do support (`A` denotes a literal character, period
+(`.`), or a single `\\ ` escape sequence; `x` and `y` denote regular
+expressions.):
+
+Expression | Meaning
+---------- | --------------------------------------------------------------
+`c`        | matches any literal character `c`
+`\\d`      | matches any decimal digit
+`\\D`      | matches any character that's not a decimal digit
+`\\f`      | matches `\f`
+`\\n`      | matches `\n`
+`\\r`      | matches `\r`
+`\\s`      | matches any ASCII whitespace, including `\n`
+`\\S`      | matches any character that's not a whitespace
+`\\t`      | matches `\t`
+`\\v`      | matches `\v`
+`\\w`      | matches any letter, `_`, or decimal digit
+`\\W`      | matches any character that `\\w` doesn't match
+`\\c`      | matches any literal character `c`, which must be a punctuation
+`.`        | matches any single character except `\n`
+`A?`       | matches 0 or 1 occurrences of `A`
+`A*`       | matches 0 or many occurrences of `A`
+`A+`       | matches 1 or many occurrences of `A`
+`^`        | matches the beginning of a string (not that of each line)
+`$`        | matches the end of a string (not that of each line)
+`xy`       | matches `x` followed by `y`
+
+To help you determine which capability is available on your system, GoogleTest
+defines macros to govern which regular expression it is using. The macros are:
+`GTEST_USES_SIMPLE_RE=1` or `GTEST_USES_POSIX_RE=1`. If you want your death
+tests to work in all cases, you can either `#if` on these macros or use the more
+limited syntax only.
+
 ## Death Tests
 
 In many applications, there are assertions that can cause application failure if
@@ -509,51 +554,6 @@ TEST_F(FooDeathTest, DoesThat) {
 }
 ```
 
-### Regular Expression Syntax
-
-When built with Bazel and using Abseil, GoogleTest uses the
-[RE2](https://github.com/google/re2/wiki/Syntax) syntax. Otherwise, for POSIX
-systems (Linux, Cygwin, Mac), GoogleTest uses the
-[POSIX extended regular expression](https://pubs.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap09.html#tag_09_04)
-syntax. To learn about POSIX syntax, you may want to read this
-[Wikipedia entry](https://en.wikipedia.org/wiki/Regular_expression#POSIX_extended).
-
-On Windows, GoogleTest uses its own simple regular expression implementation. It
-lacks many features. For example, we don't support union (`"x|y"`), grouping
-(`"(xy)"`), brackets (`"[xy]"`), and repetition count (`"x{5,7}"`), among
-others. Below is what we do support (`A` denotes a literal character, period
-(`.`), or a single `\\ ` escape sequence; `x` and `y` denote regular
-expressions.):
-
-Expression | Meaning
----------- | --------------------------------------------------------------
-`c`        | matches any literal character `c`
-`\\d`      | matches any decimal digit
-`\\D`      | matches any character that's not a decimal digit
-`\\f`      | matches `\f`
-`\\n`      | matches `\n`
-`\\r`      | matches `\r`
-`\\s`      | matches any ASCII whitespace, including `\n`
-`\\S`      | matches any character that's not a whitespace
-`\\t`      | matches `\t`
-`\\v`      | matches `\v`
-`\\w`      | matches any letter, `_`, or decimal digit
-`\\W`      | matches any character that `\\w` doesn't match
-`\\c`      | matches any literal character `c`, which must be a punctuation
-`.`        | matches any single character except `\n`
-`A?`       | matches 0 or 1 occurrences of `A`
-`A*`       | matches 0 or many occurrences of `A`
-`A+`       | matches 1 or many occurrences of `A`
-`^`        | matches the beginning of a string (not that of each line)
-`$`        | matches the end of a string (not that of each line)
-`xy`       | matches `x` followed by `y`
-
-To help you determine which capability is available on your system, GoogleTest
-defines macros to govern which regular expression it is using. The macros are:
-`GTEST_USES_SIMPLE_RE=1` or `GTEST_USES_POSIX_RE=1`. If you want your death
-tests to work in all cases, you can either `#if` on these macros or use the more
-limited syntax only.
-
 ### How It Works
 
 See [Death Assertions](reference/assertions.md#death) in the Assertions