tests/test-eol-update.t

upgrade: move descriptions and selection logic in individual classes

Our goal here is to get top level definition for all the format variants. Having
them defined outside of the function enabled other users of that logic.

They are two keys components of a format variant:

1) the name and various descriptions of its effect,

2) the code that checks if the repo is using this variant and if the config
   enables it.

That second items make us pick a class-based approach, since different variants
requires different code (even if in practice, many can reuse the same logic).
Each variants define its own class that is then used like a singleton.  The
class-based approach also clarify the definitions part a bit since each are
simple assignment in an indented block.

The 'fromdefault' and 'fromconfig' are respectively replaced by a class
attribute and a method to be called at the one place where "fromconfig"
matters.

Overall, they are many viable approach for this, but this is the one I picked.

Test EOL update

  $ cat >> $HGRCPATH <<EOF
  > [diff]
  > git = 1
  > EOF

  $ seteol () {
  >     if [ $1 = "LF" ]; then
  >         EOL='\n'
  >     else
  >         EOL='\r\n'
  >     fi
  > }

  $ makerepo () {
  >     echo
  >     echo "# ==== setup repository ===="
  >     echo '% hg init'
  >     hg init repo
  >     cd repo
  > 
  >     cat > .hgeol <<EOF
  > [patterns]
  > **.txt = LF
  > EOF
  > 
  >     printf "first\nsecond\nthird\n" > a.txt
  >     hg commit --addremove -m 'LF commit'
  > 
  >     cat > .hgeol <<EOF
  > [patterns]
  > **.txt = CRLF
  > EOF
  > 
  >     printf "first\r\nsecond\r\nthird\r\n" > a.txt
  >     hg commit -m 'CRLF commit'
  > 
  >     cd ..
  > }

  $ dotest () {
  >     seteol $1
  > 
  >     echo
  >     echo "% hg clone repo repo-$1"
  >     hg clone --noupdate repo repo-$1
  >     cd repo-$1
  > 
  >     cat > .hg/hgrc <<EOF
  > [extensions]
  > eol =
  > EOF
  > 
  >     hg update
  > 
  >     echo '% a.txt (before)'
  >     cat a.txt
  > 
  >     printf "first${EOL}third${EOL}" > a.txt
  > 
  >     echo '% a.txt (after)'
  >     cat a.txt
  >     echo '% hg diff'
  >     hg diff
  > 
  >     echo '% hg update 0'
  >     hg update 0
  > 
  >     echo '% a.txt'
  >     cat a.txt
  >     echo '% hg diff'
  >     hg diff
  > 
  > 
  >     cd ..
  >     rm -r repo-$1
  > }

  $ makerepo
  
  # ==== setup repository ====
  % hg init
  adding .hgeol
  adding a.txt
  $ dotest LF
  
  % hg clone repo repo-LF
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  % a.txt (before)
  first\r (esc)
  second\r (esc)
  third\r (esc)
  % a.txt (after)
  first
  third
  % hg diff
  diff --git a/a.txt b/a.txt
  --- a/a.txt
  +++ b/a.txt
  @@ -1,3 +1,2 @@
   first\r (esc)
  -second\r (esc)
   third\r (esc)
  % hg update 0
  merging a.txt
  1 files updated, 1 files merged, 0 files removed, 0 files unresolved
  % a.txt
  first
  third
  % hg diff
  diff --git a/a.txt b/a.txt
  --- a/a.txt
  +++ b/a.txt
  @@ -1,3 +1,2 @@
   first
  -second
   third
  $ dotest CRLF
  
  % hg clone repo repo-CRLF
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  % a.txt (before)
  first\r (esc)
  second\r (esc)
  third\r (esc)
  % a.txt (after)
  first\r (esc)
  third\r (esc)
  % hg diff
  diff --git a/a.txt b/a.txt
  --- a/a.txt
  +++ b/a.txt
  @@ -1,3 +1,2 @@
   first\r (esc)
  -second\r (esc)
   third\r (esc)
  % hg update 0
  merging a.txt
  1 files updated, 1 files merged, 0 files removed, 0 files unresolved
  % a.txt
  first
  third
  % hg diff
  diff --git a/a.txt b/a.txt
  --- a/a.txt
  +++ b/a.txt
  @@ -1,3 +1,2 @@
   first
  -second
   third
  $ rm -r repo