checkout: learn to respect checkout.guess

The current behavior of git checkout/switch is that --guess is currently
enabled by default. However, some users may not wish for this to happen
automatically. Instead of forcing users to specify --no-guess manually
each time, teach these commands the checkout.guess configuration
variable that gives users the option to set a default behavior.

Teach the completion script to recognize the new config variable and
disable DWIM logic if it is set to false.
Signed-off-by: NDenton Liu <liu.denton@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Documentation/config/checkout.txt

@@ -16,3 +16,8 @@ will checkout the `<something>` branch on another remote,
 and by linkgit:git-worktree[1] when `git worktree add` refers to a
 remote branch. This setting might be used for other checkout-like
 commands or functionality in the future.
+
+checkout.guess::
+	Provides the default value for the `--guess` or `--no-guess`
+	option in `git checkout` and `git switch`. See
+	linkgit:git-switch[1] and linkgit:git-checkout[1].

Documentation/git-checkout.txt

@@ -192,7 +192,10 @@ branches from there if `<branch>` is ambiguous but exists on the
 'origin' remote. See also `checkout.defaultRemote` in
 linkgit:git-config[1].
 +
-Use `--no-guess` to disable this.
+`--guess` is the default behavior. Use `--no-guess` to disable it.
++
+The default behavior can be set via the `checkout.guess` configuration
+variable.
 
 -l::
 	Create the new branch's reflog; see linkgit:git-branch[1] for

Documentation/git-switch.txt

@@ -103,6 +103,9 @@ ambiguous but exists on the 'origin' remote. See also
 `checkout.defaultRemote` in linkgit:git-config[1].
 +
 `--guess` is the default behavior. Use `--no-guess` to disable it.
++
+The default behavior can be set via the `checkout.guess` configuration
+variable.
 
 -f::
 --force::

builtin/checkout.c

@@ -1093,11 +1093,16 @@ static int switch_branches(const struct checkout_opts *opts,
 
 static int git_checkout_config(const char *var, const char *value, void *cb)
 {
+	struct checkout_opts *opts = cb;
+
 	if (!strcmp(var, "diff.ignoresubmodules")) {
-		struct checkout_opts *opts = cb;
 		handle_ignore_submodules_arg(&opts->diff_options, value);
 		return 0;
 	}
+	if (!strcmp(var, "checkout.guess")) {
+		opts->dwim_new_local_branch = git_config_bool(var, value);
+		return 0;
+	}
 
 	if (starts_with(var, "submodule."))
 		return git_default_submodule_config(var, value, NULL);

contrib/completion/git-completion.bash

@@ -1467,14 +1467,15 @@ _git_bundle ()
 # Helper function to decide whether or not we should enable DWIM logic for
 # git-switch and git-checkout.
 #
-# To decide between the following rules in priority order
-# 1) the last provided of "--guess" or "--no-guess" explicitly enable or
-#    disable completion of DWIM logic respectively.
-# 2) If the --no-track option is provided, take this as a hint to disable the
-#    DWIM completion logic
-# 3) If GIT_COMPLETION_CHECKOUT_NO_GUESS is set, disable the DWIM completion
-#    logic, as requested by the user.
-# 4) Enable DWIM logic otherwise.
+# To decide between the following rules in decreasing priority order:
+# - the last provided of "--guess" or "--no-guess" explicitly enable or
+#   disable completion of DWIM logic respectively.
+# - If checkout.guess is false, disable completion of DWIM logic.
+# - If the --no-track option is provided, take this as a hint to disable the
+#   DWIM completion logic
+# - If GIT_COMPLETION_CHECKOUT_NO_GUESS is set, disable the DWIM completion
+#   logic, as requested by the user.
+# - Enable DWIM logic otherwise.
 #
 __git_checkout_default_dwim_mode ()
 {
@@ -1485,11 +1486,17 @@ __git_checkout_default_dwim_mode ()
 	fi
 
 	# --no-track disables DWIM, but with lower priority than
-	# --guess/--no-guess
+	# --guess/--no-guess/checkout.guess
 	if [ -n "$(__git_find_on_cmdline "--no-track")" ]; then
 		dwim_opt=""
 	fi
 
+	# checkout.guess = false disables DWIM, but with lower priority than
+	# --guess/--no-guess
+	if [ "$(__git config --type=bool checkout.guess)" = "false" ]; then
+		dwim_opt=""
+	fi
+
 	# Find the last provided --guess or --no-guess
 	last_option="$(__git_find_last_on_cmdline "--guess --no-guess")"
 	case "$last_option" in

t/t2024-checkout-dwim.sh

@@ -166,6 +166,17 @@ test_expect_success '--no-guess suppresses branch auto-vivification' '
 	test_branch master
 '
 
+test_expect_success 'checkout.guess = false suppresses branch auto-vivification' '
+	git checkout -B master &&
+	status_uno_is_clean &&
+	test_might_fail git branch -D bar &&
+
+	test_config checkout.guess false &&
+	test_must_fail git checkout bar &&
+	test_must_fail git rev-parse --verify refs/heads/bar &&
+	test_branch master
+'
+
 test_expect_success 'setup more remotes with unconventional refspecs' '
 	git checkout -B master &&
 	status_uno_is_clean &&

t/t2060-switch.sh

@@ -85,9 +85,12 @@ test_expect_success 'switching ignores file of same branch name' '
 	test_cmp expected actual
 '
 
-test_expect_success 'guess and create branch ' '
+test_expect_success 'guess and create branch' '
 	test_when_finished git switch master &&
 	test_must_fail git switch --no-guess foo &&
+	test_config checkout.guess false &&
+	test_must_fail git switch foo &&
+	test_config checkout.guess true &&
 	git switch foo &&
 	echo refs/heads/foo >expected &&
 	git symbolic-ref HEAD >actual &&

t/t9902-completion.sh

@@ -1360,6 +1360,58 @@ test_expect_success 'git checkout - a later --no-guess overrides previous --gues
 	EOF
 '
 
+test_expect_success 'git checkout - with checkout.guess = false, only completes refs' '
+	test_config checkout.guess false &&
+	test_completion "git checkout " <<-\EOF
+	HEAD Z
+	master Z
+	matching-branch Z
+	matching-tag Z
+	other/branch-in-other Z
+	other/master-in-other Z
+	EOF
+'
+
+test_expect_success 'git checkout - with checkout.guess = true, completes refs and unique remote branches for DWIM' '
+	test_config checkout.guess true &&
+	test_completion "git checkout " <<-\EOF
+	HEAD Z
+	branch-in-other Z
+	master Z
+	master-in-other Z
+	matching-branch Z
+	matching-tag Z
+	other/branch-in-other Z
+	other/master-in-other Z
+	EOF
+'
+
+test_expect_success 'git checkout - a later --guess overrides previous checkout.guess = false, complete refs and unique remote branches for DWIM' '
+	test_config checkout.guess false &&
+	test_completion "git checkout --guess " <<-\EOF
+	HEAD Z
+	branch-in-other Z
+	master Z
+	master-in-other Z
+	matching-branch Z
+	matching-tag Z
+	other/branch-in-other Z
+	other/master-in-other Z
+	EOF
+'
+
+test_expect_success 'git checkout - a later --no-guess overrides previous checkout.guess = true, complete only refs' '
+	test_config checkout.guess true &&
+	test_completion "git checkout --no-guess " <<-\EOF
+	HEAD Z
+	master Z
+	matching-branch Z
+	matching-tag Z
+	other/branch-in-other Z
+	other/master-in-other Z
+	EOF
+'
+
 test_expect_success 'git switch - with --detach, complete all references' '
 	test_completion "git switch --detach " <<-\EOF
 	HEAD Z