Merge branch 'jn/ssh-wrappers'

The ssh-variant 'simple' introduced earlier broke existing
installations by not passing --port/-4/-6 and not diagnosing an
attempt to pass these as an error.  Instead, default to
automatically detect how compatible the GIT_SSH/GIT_SSH_COMMAND is
to OpenSSH convention and then error out an invocation to make it
easier to diagnose connection errors.

* jn/ssh-wrappers:
connect: correct style of C-style comment
ssh: 'simple' variant does not support --port
ssh: 'simple' variant does not support -4/-6
ssh: 'auto' variant to select between 'ssh' and 'simple'
connect: split ssh option computation to its own function
connect: split ssh command line options into separate function
connect: split git:// setup into a separate function
connect: move no_fork fallback to git_tcp_connect
ssh test: make copy_ssh_wrapper_as clean up after itself

diff --cc Documentation/config.txt
Simple merge

diff --cc t/t5601-clone.sh
index ef94af9fccf1f76f4b0b86994ea823a37e996b33,66784fc8ff2ec8cf24cdb70348e70995c333d233..0f895478f02bcf4cc4408ce065e79e0314b66793
--- 1/t/t5601-clone.sh
--- 2/t/t5601-clone.sh
+++ b/t/t5601-clone.sh
@@@ -306,23 -306,20 +306,21 @@@ test_expect_success 'clone checking ou
        test_cmp fetch.expected fetch.actual
  '
  
- setup_ssh_wrapper () {
-       test_expect_success 'setup ssh wrapper' '
-               rm -f "$TRASH_DIRECTORY/ssh$X" &&
-               cp "$GIT_BUILD_DIR/t/helper/test-fake-ssh$X" \
-                       "$TRASH_DIRECTORY/ssh$X" &&
-               GIT_SSH="$TRASH_DIRECTORY/ssh$X" &&
-               export GIT_SSH &&
-               export TRASH_DIRECTORY &&
-               >"$TRASH_DIRECTORY"/ssh-output
-       '
- }
+ test_expect_success 'set up ssh wrapper' '
+       cp "$GIT_BUILD_DIR/t/helper/test-fake-ssh$X" \
+               "$TRASH_DIRECTORY/ssh$X" &&
+       GIT_SSH="$TRASH_DIRECTORY/ssh$X" &&
+       export GIT_SSH &&
+       export TRASH_DIRECTORY &&
+       >"$TRASH_DIRECTORY"/ssh-output
+ '
  
  copy_ssh_wrapper_as () {
 +      rm -f "${1%$X}$X" &&
        cp "$TRASH_DIRECTORY/ssh$X" "${1%$X}$X" &&
+       test_when_finished "rm $(git rev-parse --sq-quote "${1%$X}$X")" &&
        GIT_SSH="${1%$X}$X" &&
-       export GIT_SSH
+       test_when_finished "GIT_SSH=\"\$TRASH_DIRECTORY/ssh\$X\""
  }
  
  expect_ssh () {