tests/test-diff-indent-heuristic.t

rhg: Port Python’s `ui.configlist` as `Config::get_list`

This new method is not used yet outside of its own unit tests,
so this changeset should make no observable change.

The Rust parser implementation attempts to exactly replicate the behavior of
the Python one, even in edge cases where that behavior is… surprising.
New unit tests capture some of these edge cases.

This started as a line-by-line port. The main changes are:

* Pass around a parser mode enum instead of parser functions
* Inline the whole parser into one function
* Use `[u8]::get` which returns an `Option`,
  instead of indexing  after explicitly checking the length.

Differential Revision: https://phab.mercurial-scm.org/D11389

#testcases bdiff xdiff

#if xdiff
#require xdiff
  $ cat >> $HGRCPATH <<EOF
  > [experimental]
  > xdiff = true
  > EOF
#endif

  $ hg init

  $ cat > a.c <<'EOF'
  > /*
  >  * This function returns 1.
  >  */
  > int f() {
  >   return 1;
  > }
  > /*
  >  * This function returns 2.
  >  */
  > int g() {
  >   return 2;
  > }
  > /*
  >  * This function returns 3.
  >  */
  > int h() {
  >   return 3;
  > }
  > EOF

  $ cat > b.c <<'EOF'
  > if (x) {
  >    do_something();
  > }
  > 
  > if (y) {
  >    do_something_else();
  > }
  > EOF

  $ cat > c.rb <<'EOF'
  > #!ruby
  > ["foo", "bar", "baz"].map do |i|
  >   i.upcase
  > end
  > EOF

  $ cat > d.py <<'EOF'
  > try:
  >     import foo
  > except ImportError:
  >     pass
  > try:
  >     import bar
  > except ImportError:
  >     pass
  > EOF

The below two files are taken from git: t/t4061-diff-indent.sh

  $ cat > spaces.txt <<'EOF'
  > 1
  > 2
  > a
  > 
  > b
  > 3
  > 4
  > EOF

  $ cat > functions.c <<'EOF'
  > 1
  > 2
  > /* function */
  > foo() {
  >     foo
  > }
  > 
  > 3
  > 4
  > EOF

  $ hg commit -m 1 -A . -q

  $ cat > a.c <<'EOF'
  > /*
  >  * This function returns 1.
  >  */
  > int f() {
  >   return 1;
  > }
  > /*
  >  * This function returns 3.
  >  */
  > int h() {
  >   return 3;
  > }
  > EOF

  $ cat > b.c <<'EOF'
  > if (x) {
  >    do_something();
  > }
  > 
  > if (y) {
  >    do_another_thing();
  > }
  > 
  > if (y) {
  >    do_something_else();
  > }
  > EOF

  $ cat > c.rb <<'EOF'
  > #!ruby
  > ["foo", "bar", "baz"].map do |i|
  >   i
  > end
  > ["foo", "bar", "baz"].map do |i|
  >   i.upcase
  > end
  > EOF

  $ cat > d.py <<'EOF'
  > try:
  >     import foo
  > except ImportError:
  >     pass
  > try:
  >     import baz
  > except ImportError:
  >     pass
  > try:
  >     import bar
  > except ImportError:
  >     pass
  > EOF

  $ cat > spaces.txt <<'EOF'
  > 1
  > 2
  > a
  > 
  > b
  > a
  > 
  > b
  > 3
  > 4
  > EOF

  $ cat > functions.c <<'EOF'
  > 1
  > 2
  > /* function */
  > bar() {
  >     foo
  > }
  > 
  > /* function */
  > foo() {
  >     foo
  > }
  > 
  > 3
  > 4
  > EOF

#if xdiff
  $ hg diff --git
  diff --git a/a.c b/a.c
  --- a/a.c
  +++ b/a.c
  @@ -4,12 +4,6 @@
   int f() {
     return 1;
   }
  -/*
  - * This function returns 2.
  - */
  -int g() {
  -  return 2;
  -}
   /*
    * This function returns 3.
    */
  diff --git a/b.c b/b.c
  --- a/b.c
  +++ b/b.c
  @@ -2,6 +2,10 @@
      do_something();
   }
   
  +if (y) {
  +   do_another_thing();
  +}
  +
   if (y) {
      do_something_else();
   }
  diff --git a/c.rb b/c.rb
  --- a/c.rb
  +++ b/c.rb
  @@ -1,4 +1,7 @@
   #!ruby
  +["foo", "bar", "baz"].map do |i|
  +  i
  +end
   ["foo", "bar", "baz"].map do |i|
     i.upcase
   end
  diff --git a/d.py b/d.py
  --- a/d.py
  +++ b/d.py
  @@ -2,6 +2,10 @@
       import foo
   except ImportError:
       pass
  +try:
  +    import baz
  +except ImportError:
  +    pass
   try:
       import bar
   except ImportError:
  diff --git a/functions.c b/functions.c
  --- a/functions.c
  +++ b/functions.c
  @@ -1,5 +1,10 @@
   1
   2
  +/* function */
  +bar() {
  +    foo
  +}
  +
   /* function */
   foo() {
       foo
  diff --git a/spaces.txt b/spaces.txt
  --- a/spaces.txt
  +++ b/spaces.txt
  @@ -2,6 +2,9 @@
   2
   a
   
  +b
  +a
  +
   b
   3
   4
#else
  $ hg diff --git
  diff --git a/a.c b/a.c
  --- a/a.c
  +++ b/a.c
  @@ -5,12 +5,6 @@
     return 1;
   }
   /*
  - * This function returns 2.
  - */
  -int g() {
  -  return 2;
  -}
  -/*
    * This function returns 3.
    */
   int h() {
  diff --git a/b.c b/b.c
  --- a/b.c
  +++ b/b.c
  @@ -3,5 +3,9 @@
   }
   
   if (y) {
  +   do_another_thing();
  +}
  +
  +if (y) {
      do_something_else();
   }
  diff --git a/c.rb b/c.rb
  --- a/c.rb
  +++ b/c.rb
  @@ -1,4 +1,7 @@
   #!ruby
   ["foo", "bar", "baz"].map do |i|
  +  i
  +end
  +["foo", "bar", "baz"].map do |i|
     i.upcase
   end
  diff --git a/d.py b/d.py
  --- a/d.py
  +++ b/d.py
  @@ -3,6 +3,10 @@
   except ImportError:
       pass
   try:
  +    import baz
  +except ImportError:
  +    pass
  +try:
       import bar
   except ImportError:
       pass
  diff --git a/functions.c b/functions.c
  --- a/functions.c
  +++ b/functions.c
  @@ -1,6 +1,11 @@
   1
   2
   /* function */
  +bar() {
  +    foo
  +}
  +
  +/* function */
   foo() {
       foo
   }
  diff --git a/spaces.txt b/spaces.txt
  --- a/spaces.txt
  +++ b/spaces.txt
  @@ -3,5 +3,8 @@
   a
   
   b
  +a
  +
  +b
   3
   4
#endif