[PATCH] worktree add: shouldn't dwim if -b or -B is given

[PATCH] worktree add: shouldn't dwim if -b or -B is given

[Yoichi NAKAYAMA via GitGitGadget]

From: Yoichi NAKAYAMA <yoichi.nakayama@gmail.com>

'git worktree add <path> <branch>' DWIMs <branch> to a
remote-tracking branch when neither -b, -B, nor --detach
is given.

However, 'git worktree add -b <new-branch> <path> <branch>' can
still DWIM <branch>, causing <new-branch> to be ignored.

This is a regression introduced in v2.42.0
(128e5496b325640f0a09cc1d5b1e346c069b410f).

Signed-off-by: Yoichi NAKAYAMA <yoichi.nakayama@gmail.com>
---
    worktree add: shouldn't dwim if -b or -B is given

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-2192%2Fyoichi%2Fworktree-add-should-not-dwim-with-b-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-2192/yoichi/worktree-add-should-not-dwim-with-b-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/2192

 builtin/worktree.c      |  2 +-
 t/t2400-worktree-add.sh | 10 ++++++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/builtin/worktree.c b/builtin/worktree.c
index 654d27c3e1..3204afdb12 100644
--- a/builtin/worktree.c
+++ b/builtin/worktree.c
@@ -897,7 +897,7 @@ static int add(int ac, const char **av, const char *prefix,
 
 		/* DWIM: Infer --orphan when repo has no refs. */
 		opts.orphan = (!s) && dwim_orphan(&opts, !!opt_track, 1);
-	} else if (ac == 2) {
+	} else if (ac == 2 && !new_branch) {
 		struct object_id oid;
 		struct commit *commit;
 		char *remote;
diff --git a/t/t2400-worktree-add.sh b/t/t2400-worktree-add.sh
index 87b926728a..9cbf84861d 100755
--- a/t/t2400-worktree-add.sh
+++ b/t/t2400-worktree-add.sh
@@ -621,6 +621,16 @@ test_expect_success '"add" <path> <branch> dwims' '
 	)
 '
 
+test_expect_success '"add" <path> <branch> does not dwim with -b' '
+	test_when_finished rm -rf repo_upstream repo_dwim foo &&
+	setup_remote_repo repo_upstream repo_dwim &&
+	git init repo_dwim &&
+	(
+		cd repo_dwim &&
+		test_must_fail git worktree add -b branch ../foo foo
+	)
+'
+
 test_expect_success '"add" <path> <branch> dwims with checkout.defaultRemote' '
 	test_when_finished rm -rf repo_upstream repo_dwim foo &&
 	setup_remote_repo repo_upstream repo_dwim &&

base-commit: 5b2471720c93ee30e5764a19f3d3b3ae9ec9712a
-- 
gitgitgadget

Re: [PATCH] worktree add: shouldn't dwim if -b or -B is given

[Junio C Hamano]

"Yoichi NAKAYAMA via GitGitGadget" <gitgitgadget@gmail.com> writes:

> From: Yoichi NAKAYAMA <yoichi.nakayama@gmail.com>
>
> 'git worktree add <path> <branch>' DWIMs <branch> to a
> remote-tracking branch when neither -b, -B, nor --detach
> is given.
>
> However, 'git worktree add -b <new-branch> <path> <branch>' can
> still DWIM <branch>, causing <new-branch> to be ignored.
>
> This is a regression introduced in v2.42.0
> (128e5496b325640f0a09cc1d5b1e346c069b410f).
>
> Signed-off-by: Yoichi NAKAYAMA <yoichi.nakayama@gmail.com>
> ---
>     worktree add: shouldn't dwim if -b or -B is given
>
> Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-2192%2Fyoichi%2Fworktree-add-should-not-dwim-with-b-v1
> Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-2192/yoichi/worktree-add-should-not-dwim-with-b-v1
> Pull-Request: https://github.com/gitgitgadget/git/pull/2192
>
>  builtin/worktree.c      |  2 +-
>  t/t2400-worktree-add.sh | 10 ++++++++++
>  2 files changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/builtin/worktree.c b/builtin/worktree.c
> index 654d27c3e1..3204afdb12 100644
> --- a/builtin/worktree.c
> +++ b/builtin/worktree.c
> @@ -897,7 +897,7 @@ static int add(int ac, const char **av, const char *prefix,
>  
>  		/* DWIM: Infer --orphan when repo has no refs. */
>  		opts.orphan = (!s) && dwim_orphan(&opts, !!opt_track, 1);
> -	} else if (ac == 2) {
> +	} else if (ac == 2 && !new_branch) {
>  		struct object_id oid;
>  		struct commit *commit;
>  		char *remote;

This part checks 'branch' (assigned from av[1] earlier) to see if it
names a commit.  When it does not, the code checks if it is the name
of a unique remote-tracking branch; if it is, the code uses that as
'branch', which is the origin to be used to fork 'new_branch' (av[1]
in this case) from.

Your observation is correct that this would overwrite 'new_branch'
if it were supplied.

Stepping back a bit, though, does this change the behavior when
'branch' *does* resolve to a commit (hence, the DWIM is already
bypassed and 'new_branch' or 'branch' are not nuked)?  When 'ac' is
equal to 2 and 'new_branch' is supplied, we used to call:

        if (!strcmp(branch, "HEAD"))
                can_use_local_refs(&opts);

inside the block you are now skipping.  It looks to me that this
patch also changes behavior when the user says:

        $ git worktree add -b <new-branch> <path> HEAD

by not calling can_use_local_refs(), whose only effect in this
context is that it may issue a warning() to the user.  I do not know
offhand what the ramifications of this difference are.

I wonder if we want to skip only the dwim part inside of this "else if"
arm, e.g.

diff --git i/builtin/worktree.c w/builtin/worktree.c
index 654d27c3e1..2205f4e9b2 100644
--- i/builtin/worktree.c
+++ w/builtin/worktree.c
@@ -898,6 +898,7 @@ static int add(int ac, const char **av, const char *prefix,
 		/* DWIM: Infer --orphan when repo has no refs. */
 		opts.orphan = (!s) && dwim_orphan(&opts, !!opt_track, 1);
 	} else if (ac == 2) {
+	    if (!newbranch) {
 		struct object_id oid;
 		struct commit *commit;
 		char *remote;
@@ -910,6 +911,7 @@ static int add(int ac, const char **av, const char *prefix,
 				branch = new_branch_to_free = remote;
 			}
 		}
+	    }
 
 		if (!strcmp(branch, "HEAD"))
 			can_use_local_refs(&opts);

Note that above diff is with broken indentation to help reduce the
patch noise to illustrate where the new block boundary would be.

> diff --git a/t/t2400-worktree-add.sh b/t/t2400-worktree-add.sh
> index 87b926728a..9cbf84861d 100755
> --- a/t/t2400-worktree-add.sh
> +++ b/t/t2400-worktree-add.sh
> @@ -621,6 +621,16 @@ test_expect_success '"add" <path> <branch> dwims' '
>  	)
>  '
>  
> +test_expect_success '"add" <path> <branch> does not dwim with -b' '
> +	test_when_finished rm -rf repo_upstream repo_dwim foo &&
> +	setup_remote_repo repo_upstream repo_dwim &&
> +	git init repo_dwim &&
> +	(
> +		cd repo_dwim &&
> +		test_must_fail git worktree add -b branch ../foo foo
> +	)
> +'

Two comments.

 * You call setup_remote_repo(), which takes two names, runs
   'git init' on each of them, and prepares those repositories.  Do
   you need to run 'git init repo_dwim' to initialize it again?
   What for?

 * Expecting a failure to create a worktree may be fine, but can we
   say how we expect the command to fail as well?  Perhaps you can
   capture the error message while ensuring that the command fails,
   and then check the error message to make sure it failed in the
   expected way, or something like that.

Thanks.

Re: [PATCH] worktree add: shouldn't dwim if -b or -B is given

[Yoichi Nakayama]

On Wed, Aug 5, 2026 at 2:11 AM Junio C Hamano <gitster@pobox.com> wrote:
> Stepping back a bit, though, does this change the behavior when
> 'branch' *does* resolve to a commit (hence, the DWIM is already
> bypassed and 'new_branch' or 'branch' are not nuked)?  When 'ac' is
> equal to 2 and 'new_branch' is supplied, we used to call:
>
>         if (!strcmp(branch, "HEAD"))
>                 can_use_local_refs(&opts);
>
> inside the block you are now skipping.  It looks to me that this
> patch also changes behavior when the user says:
>
>         $ git worktree add -b <new-branch> <path> HEAD
>
> by not calling can_use_local_refs(), whose only effect in this
> context is that it may issue a warning() to the user.  I do not know
> offhand what the ramifications of this difference are.

It is better to emit warnings for the given arguments whenever possible,
so I think we should not skip the step mentioned above.
I'll modify the condition.

> > diff --git a/t/t2400-worktree-add.sh b/t/t2400-worktree-add.sh
> > index 87b926728a..9cbf84861d 100755
> > --- a/t/t2400-worktree-add.sh
> > +++ b/t/t2400-worktree-add.sh
> > @@ -621,6 +621,16 @@ test_expect_success '"add" <path> <branch> dwims' '
> >       )
> >  '
> >
> > +test_expect_success '"add" <path> <branch> does not dwim with -b' '
> > +     test_when_finished rm -rf repo_upstream repo_dwim foo &&
> > +     setup_remote_repo repo_upstream repo_dwim &&
> > +     git init repo_dwim &&
> > +     (
> > +             cd repo_dwim &&
> > +             test_must_fail git worktree add -b branch ../foo foo
> > +     )
> > +'
>
> Two comments.
>
>  * You call setup_remote_repo(), which takes two names, runs
>    'git init' on each of them, and prepares those repositories.  Do
>    you need to run 'git init repo_dwim' to initialize it again?
>    What for?

'git init' was unnecessary.  It was included because I copied
an existing test; I'll remove it.

>  * Expecting a failure to create a worktree may be fine, but can we
>    say how we expect the command to fail as well?  Perhaps you can
>    capture the error message while ensuring that the command fails,
>    and then check the error message to make sure it failed in the
>    expected way, or something like that.

Expected error is 'fatal: invalid reference: foo'. I'll add test_grep.

Thanks,
-- 
Yoichi NAKAYAMA

[PATCH v2] worktree add: shouldn't dwim if -b or -B is given

[Yoichi NAKAYAMA via GitGitGadget]

From: Yoichi NAKAYAMA <yoichi.nakayama@gmail.com>

git worktree add <path> <branch> DWIMs <branch> to a
remote-tracking branch when neither -b, -B, nor --detach
is given.

However, git worktree add -b <new-branch> <path> <branch> can
still DWIM <branch>, causing <new-branch> to be ignored.

This is a regression introduced in v2.42.0
(128e5496b325640f0a09cc1d5b1e346c069b410f).

Signed-off-by: Yoichi NAKAYAMA <yoichi.nakayama@gmail.com>
---
    worktree add: shouldn't dwim if -b or -B is given

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-2192%2Fyoichi%2Fworktree-add-should-not-dwim-with-b-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-2192/yoichi/worktree-add-should-not-dwim-with-b-v2
Pull-Request: https://github.com/gitgitgadget/git/pull/2192

Range-diff vs v1:

 1:  908a32fb56 ! 1:  b00f6c2fa1 worktree add: shouldn't dwim if -b or -B is given
     @@ Metadata
       ## Commit message ##
          worktree add: shouldn't dwim if -b or -B is given
      
     -    'git worktree add <path> <branch>' DWIMs <branch> to a
     +    git worktree add <path> <branch> DWIMs <branch> to a
          remote-tracking branch when neither -b, -B, nor --detach
          is given.
      
     -    However, 'git worktree add -b <new-branch> <path> <branch>' can
     +    However, git worktree add -b <new-branch> <path> <branch> can
          still DWIM <branch>, causing <new-branch> to be ignored.
      
          This is a regression introduced in v2.42.0
     @@ Commit message
      
       ## builtin/worktree.c ##
      @@ builtin/worktree.c: static int add(int ac, const char **av, const char *prefix,
     - 
       		/* DWIM: Infer --orphan when repo has no refs. */
       		opts.orphan = (!s) && dwim_orphan(&opts, !!opt_track, 1);
     --	} else if (ac == 2) {
     -+	} else if (ac == 2 && !new_branch) {
     - 		struct object_id oid;
     - 		struct commit *commit;
     - 		char *remote;
     + 	} else if (ac == 2) {
     +-		struct object_id oid;
     +-		struct commit *commit;
     +-		char *remote;
     +-
     +-		commit = lookup_commit_reference_by_name(branch);
     +-		if (!commit) {
     +-			remote = unique_tracking_name(branch, &oid, NULL);
     +-			if (remote) {
     +-				new_branch = branch;
     +-				branch = new_branch_to_free = remote;
     ++		if (!new_branch) {
     ++			struct object_id oid;
     ++			struct commit *commit;
     ++			char *remote;
     ++
     ++			commit = lookup_commit_reference_by_name(branch);
     ++			if (!commit) {
     ++				remote = unique_tracking_name(branch, &oid, NULL);
     ++				if (remote) {
     ++					new_branch = branch;
     ++					branch = new_branch_to_free = remote;
     ++				}
     + 			}
     + 		}
     + 
      
       ## t/t2400-worktree-add.sh ##
      @@ t/t2400-worktree-add.sh: test_expect_success '"add" <path> <branch> dwims' '
     @@ t/t2400-worktree-add.sh: test_expect_success '"add" <path> <branch> dwims' '
       '
       
      +test_expect_success '"add" <path> <branch> does not dwim with -b' '
     -+	test_when_finished rm -rf repo_upstream repo_dwim foo &&
     ++	test_when_finished rm -rf repo_upstream repo_dwim wt &&
      +	setup_remote_repo repo_upstream repo_dwim &&
     -+	git init repo_dwim &&
      +	(
      +		cd repo_dwim &&
     -+		test_must_fail git worktree add -b branch ../foo foo
     ++		test_must_fail git worktree add -b branch ../wt foo 2>actual &&
     ++		test_grep "^fatal: invalid reference: foo" actual
      +	)
      +'
      +


 builtin/worktree.c      | 22 ++++++++++++----------
 t/t2400-worktree-add.sh | 10 ++++++++++
 2 files changed, 22 insertions(+), 10 deletions(-)

diff --git a/builtin/worktree.c b/builtin/worktree.c
index 654d27c3e1..cc46c1b415 100644
--- a/builtin/worktree.c
+++ b/builtin/worktree.c
@@ -898,16 +898,18 @@ static int add(int ac, const char **av, const char *prefix,
 		/* DWIM: Infer --orphan when repo has no refs. */
 		opts.orphan = (!s) && dwim_orphan(&opts, !!opt_track, 1);
 	} else if (ac == 2) {
-		struct object_id oid;
-		struct commit *commit;
-		char *remote;
-
-		commit = lookup_commit_reference_by_name(branch);
-		if (!commit) {
-			remote = unique_tracking_name(branch, &oid, NULL);
-			if (remote) {
-				new_branch = branch;
-				branch = new_branch_to_free = remote;
+		if (!new_branch) {
+			struct object_id oid;
+			struct commit *commit;
+			char *remote;
+
+			commit = lookup_commit_reference_by_name(branch);
+			if (!commit) {
+				remote = unique_tracking_name(branch, &oid, NULL);
+				if (remote) {
+					new_branch = branch;
+					branch = new_branch_to_free = remote;
+				}
 			}
 		}
 
diff --git a/t/t2400-worktree-add.sh b/t/t2400-worktree-add.sh
index 87b926728a..ba3bec078f 100755
--- a/t/t2400-worktree-add.sh
+++ b/t/t2400-worktree-add.sh
@@ -621,6 +621,16 @@ test_expect_success '"add" <path> <branch> dwims' '
 	)
 '
 
+test_expect_success '"add" <path> <branch> does not dwim with -b' '
+	test_when_finished rm -rf repo_upstream repo_dwim wt &&
+	setup_remote_repo repo_upstream repo_dwim &&
+	(
+		cd repo_dwim &&
+		test_must_fail git worktree add -b branch ../wt foo 2>actual &&
+		test_grep "^fatal: invalid reference: foo" actual
+	)
+'
+
 test_expect_success '"add" <path> <branch> dwims with checkout.defaultRemote' '
 	test_when_finished rm -rf repo_upstream repo_dwim foo &&
 	setup_remote_repo repo_upstream repo_dwim &&

base-commit: 5b2471720c93ee30e5764a19f3d3b3ae9ec9712a
-- 
gitgitgadget

Re: [PATCH v2] worktree add: shouldn't dwim if -b or -B is given

[Yoichi Nakayama]

On Wed, Aug 5, 2026 at 9:16 PM Yoichi NAKAYAMA via GitGitGadget
<gitgitgadget@gmail.com> wrote:
> Range-diff vs v1:
>
>  1:  908a32fb56 ! 1:  b00f6c2fa1 worktree add: shouldn't dwim if -b or -B is given
>      @@ Metadata
>        ## Commit message ##
>           worktree add: shouldn't dwim if -b or -B is given
>
>      -    'git worktree add <path> <branch>' DWIMs <branch> to a
>      +    git worktree add <path> <branch> DWIMs <branch> to a
>           remote-tracking branch when neither -b, -B, nor --detach
>           is given.
>
>      -    However, 'git worktree add -b <new-branch> <path> <branch>' can
>      +    However, git worktree add -b <new-branch> <path> <branch> can
>           still DWIM <branch>, causing <new-branch> to be ignored.
>
>           This is a regression introduced in v2.42.0

I accidentally removed the quotes in the commit message. I'll fix it.
-- 
Yoichi NAKAYAMA

[PATCH v3] worktree add: shouldn't dwim if -b or -B is given

[Yoichi NAKAYAMA via GitGitGadget]

From: Yoichi NAKAYAMA <yoichi.nakayama@gmail.com>

'git worktree add <path> <branch>' DWIMs <branch> to a
remote-tracking branch when neither -b, -B, nor --detach
is given.

However, 'git worktree add -b <new-branch> <path> <branch>' can
still DWIM <branch>, causing <new-branch> to be ignored.

This is a regression introduced in v2.42.0
(128e5496b325640f0a09cc1d5b1e346c069b410f).

Signed-off-by: Yoichi NAKAYAMA <yoichi.nakayama@gmail.com>
---
    worktree add: shouldn't dwim if -b or -B is given

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-2192%2Fyoichi%2Fworktree-add-should-not-dwim-with-b-v3
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-2192/yoichi/worktree-add-should-not-dwim-with-b-v3
Pull-Request: https://github.com/gitgitgadget/git/pull/2192

Range-diff vs v2:

 1:  b00f6c2fa1 ! 1:  477ea27c8b worktree add: shouldn't dwim if -b or -B is given
     @@ Metadata
       ## Commit message ##
          worktree add: shouldn't dwim if -b or -B is given
      
     -    git worktree add <path> <branch> DWIMs <branch> to a
     +    'git worktree add <path> <branch>' DWIMs <branch> to a
          remote-tracking branch when neither -b, -B, nor --detach
          is given.
      
     -    However, git worktree add -b <new-branch> <path> <branch> can
     +    However, 'git worktree add -b <new-branch> <path> <branch>' can
          still DWIM <branch>, causing <new-branch> to be ignored.
      
          This is a regression introduced in v2.42.0


 builtin/worktree.c      | 22 ++++++++++++----------
 t/t2400-worktree-add.sh | 10 ++++++++++
 2 files changed, 22 insertions(+), 10 deletions(-)

diff --git a/builtin/worktree.c b/builtin/worktree.c
index 654d27c3e1..cc46c1b415 100644
--- a/builtin/worktree.c
+++ b/builtin/worktree.c
@@ -898,16 +898,18 @@ static int add(int ac, const char **av, const char *prefix,
 		/* DWIM: Infer --orphan when repo has no refs. */
 		opts.orphan = (!s) && dwim_orphan(&opts, !!opt_track, 1);
 	} else if (ac == 2) {
-		struct object_id oid;
-		struct commit *commit;
-		char *remote;
-
-		commit = lookup_commit_reference_by_name(branch);
-		if (!commit) {
-			remote = unique_tracking_name(branch, &oid, NULL);
-			if (remote) {
-				new_branch = branch;
-				branch = new_branch_to_free = remote;
+		if (!new_branch) {
+			struct object_id oid;
+			struct commit *commit;
+			char *remote;
+
+			commit = lookup_commit_reference_by_name(branch);
+			if (!commit) {
+				remote = unique_tracking_name(branch, &oid, NULL);
+				if (remote) {
+					new_branch = branch;
+					branch = new_branch_to_free = remote;
+				}
 			}
 		}
 
diff --git a/t/t2400-worktree-add.sh b/t/t2400-worktree-add.sh
index 87b926728a..ba3bec078f 100755
--- a/t/t2400-worktree-add.sh
+++ b/t/t2400-worktree-add.sh
@@ -621,6 +621,16 @@ test_expect_success '"add" <path> <branch> dwims' '
 	)
 '
 
+test_expect_success '"add" <path> <branch> does not dwim with -b' '
+	test_when_finished rm -rf repo_upstream repo_dwim wt &&
+	setup_remote_repo repo_upstream repo_dwim &&
+	(
+		cd repo_dwim &&
+		test_must_fail git worktree add -b branch ../wt foo 2>actual &&
+		test_grep "^fatal: invalid reference: foo" actual
+	)
+'
+
 test_expect_success '"add" <path> <branch> dwims with checkout.defaultRemote' '
 	test_when_finished rm -rf repo_upstream repo_dwim foo &&
 	setup_remote_repo repo_upstream repo_dwim &&

base-commit: 5b2471720c93ee30e5764a19f3d3b3ae9ec9712a
-- 
gitgitgadget

Re: [PATCH v3] worktree add: shouldn't dwim if -b or -B is given

[Junio C Hamano]

"Yoichi NAKAYAMA via GitGitGadget" <gitgitgadget@gmail.com> writes:

> From: Yoichi NAKAYAMA <yoichi.nakayama@gmail.com>
>
> 'git worktree add <path> <branch>' DWIMs <branch> to a
> remote-tracking branch when neither -b, -B, nor --detach
> is given.
>
> However, 'git worktree add -b <new-branch> <path> <branch>' can
> still DWIM <branch>, causing <new-branch> to be ignored.
>
> This is a regression introduced in v2.42.0
> (128e5496b325640f0a09cc1d5b1e346c069b410f).

I'll commit with the latter half of the above message rewritten like
this:

    However, 'git worktree add -b <new-branch> <path> <branch>' can
    still DWIM <branch>, causing <new-branch> to be ignored.  This is a
    regression introduced by 128e5496b3 (worktree add: extend DWIM to
    infer --orphan, 2023-05-17), which appeared in Git 2.42.

As we refer to an individual commit using "log -1
--pretty=reference" format.

> Signed-off-by: Yoichi NAKAYAMA <yoichi.nakayama@gmail.com>
> ---
>     worktree add: shouldn't dwim if -b or -B is given

The change looks good to me.

Thanks.

>
> Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-2192%2Fyoichi%2Fworktree-add-should-not-dwim-with-b-v3
> Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-2192/yoichi/worktree-add-should-not-dwim-with-b-v3
> Pull-Request: https://github.com/gitgitgadget/git/pull/2192
>
> Range-diff vs v2:
>
>  1:  b00f6c2fa1 ! 1:  477ea27c8b worktree add: shouldn't dwim if -b or -B is given
>      @@ Metadata
>        ## Commit message ##
>           worktree add: shouldn't dwim if -b or -B is given
>       
>      -    git worktree add <path> <branch> DWIMs <branch> to a
>      +    'git worktree add <path> <branch>' DWIMs <branch> to a
>           remote-tracking branch when neither -b, -B, nor --detach
>           is given.
>       
>      -    However, git worktree add -b <new-branch> <path> <branch> can
>      +    However, 'git worktree add -b <new-branch> <path> <branch>' can
>           still DWIM <branch>, causing <new-branch> to be ignored.
>       
>           This is a regression introduced in v2.42.0
>
>
>  builtin/worktree.c      | 22 ++++++++++++----------
>  t/t2400-worktree-add.sh | 10 ++++++++++
>  2 files changed, 22 insertions(+), 10 deletions(-)
>
> diff --git a/builtin/worktree.c b/builtin/worktree.c
> index 654d27c3e1..cc46c1b415 100644
> --- a/builtin/worktree.c
> +++ b/builtin/worktree.c
> @@ -898,16 +898,18 @@ static int add(int ac, const char **av, const char *prefix,
>  		/* DWIM: Infer --orphan when repo has no refs. */
>  		opts.orphan = (!s) && dwim_orphan(&opts, !!opt_track, 1);
>  	} else if (ac == 2) {
> -		struct object_id oid;
> -		struct commit *commit;
> -		char *remote;
> -
> -		commit = lookup_commit_reference_by_name(branch);
> -		if (!commit) {
> -			remote = unique_tracking_name(branch, &oid, NULL);
> -			if (remote) {
> -				new_branch = branch;
> -				branch = new_branch_to_free = remote;
> +		if (!new_branch) {
> +			struct object_id oid;
> +			struct commit *commit;
> +			char *remote;
> +
> +			commit = lookup_commit_reference_by_name(branch);
> +			if (!commit) {
> +				remote = unique_tracking_name(branch, &oid, NULL);
> +				if (remote) {
> +					new_branch = branch;
> +					branch = new_branch_to_free = remote;
> +				}
>  			}
>  		}
>  
> diff --git a/t/t2400-worktree-add.sh b/t/t2400-worktree-add.sh
> index 87b926728a..ba3bec078f 100755
> --- a/t/t2400-worktree-add.sh
> +++ b/t/t2400-worktree-add.sh
> @@ -621,6 +621,16 @@ test_expect_success '"add" <path> <branch> dwims' '
>  	)
>  '
>  
> +test_expect_success '"add" <path> <branch> does not dwim with -b' '
> +	test_when_finished rm -rf repo_upstream repo_dwim wt &&
> +	setup_remote_repo repo_upstream repo_dwim &&
> +	(
> +		cd repo_dwim &&
> +		test_must_fail git worktree add -b branch ../wt foo 2>actual &&
> +		test_grep "^fatal: invalid reference: foo" actual
> +	)
> +'
> +
>  test_expect_success '"add" <path> <branch> dwims with checkout.defaultRemote' '
>  	test_when_finished rm -rf repo_upstream repo_dwim foo &&
>  	setup_remote_repo repo_upstream repo_dwim &&
>
> base-commit: 5b2471720c93ee30e5764a19f3d3b3ae9ec9712a