[PATCH v3 0/4] difftools in tabbed mode

Junio C Hamano, thank you for the comment. I added the diff_combo_supported
function as you suggested. Though it calls to the `true` or the `false` builtins
as I find them much clearer than the "return" command with inverted status. It
is really confusing that C and most other programming languages adequately
interpret non-zero as truth value and zero as falsity value unlike Unix Shell.
Are such changes acceptable?

As regards broken tests, it may seem silly but that error was due to a single
missing colon. I corrected the mistake and added some automated tests of this
new feature.

diff --git a/git-difftool--helper.sh b/git-difftool--helper.sh
index 529d55c96d..85a6dc9c30 100755
--- a/git-difftool--helper.sh
+++ b/git-difftool--helper.sh

@@ -31,7 +31,7 @@ prompt_before_launch () {
 	do
 		printf "Launch '%s' [Y/n]? " "${GIT_DIFFTOOL_EXTCMD:-$merge_tool}"
 		read ans 2>/dev/null || return 1
-		case "${ans-y}" in
+		case "${ans:-y}" in
 		[yY]*) return 0 ;;
 		[nN]*) return 1 ;;
 		esac

Changes compared to v2:
 * Introduced the diff_combo_supported function.
 * Fixed default answer to difftool prompting.
 * More docs about the diff tool mechanism.
 * New auto-tests of the feature.

Nicholas Guriev (4):
  mergetools: support difftool.tabbed setting
  difftool-helper: conciliate difftool.tabbed and difftool.prompt
    settings
  doc: describe new difftool.tabbed feature
  t7800: new tests of difftool.tabbed feature

 Documentation/config/difftool.txt    |   6 +
 Documentation/git-difftool.txt       |  19 ++-
 Documentation/git-mergetool--lib.txt |  62 ++++++++++
 Documentation/git.txt                |   8 ++
 builtin/difftool.c                   |   7 +-
 diff.c                               |  10 +-
 git-difftool--helper.sh              |  39 ++++--
 git-mergetool--lib.sh                |  71 ++++++++++-
 mergetools/meld                      |   8 ++
 mergetools/vimdiff                   |  21 ++++
 t/t7800-difftool.sh                  | 175 ++++++++++++++++++++++++++-
 11 files changed, 401 insertions(+), 25 deletions(-)

-- 
2.27.0