Re: [PATCH v3 2/2] add-patch: classify '@' as a synonym for 'HEAD'
On Sun Feb 4, 2024 at 4:03 AM IST, Junio C Hamano wrote:
Show 23 quoted lines
> Ghanshyam Thakkar <shyamthakkar001@gmail.com> writes:
>
> > Therefore, make a new function user_meant_head() which takes the
> > revision string and compares it to 'HEAD' as well as '@'. However, in
> > builtin/checkout.c, there is a logic to convert all command line input
> > rev to the raw object name for underlying machinery (e.g., diff-index)
> > that does not recognize the <a>...<b> notation, but we'd need to leave
> > 'HEAD' intact. Now we need to teach that '@' is a synonym to 'HEAD'
> > to that code and leave '@' intact, too.
>
> I am not sure what that "However" wants to say.
>
> - Now we have a helper function to see what the end-user said, and
> tell if the end-user meant the state that is currently checked
> out (aka "HEAD" but some folks like a synonym "@"[*]), or if the
> end-user meant some other "concrete" branch.
>
> - In builtin/checkout.c, there is a logic to convert unless what
> the end-user meant is the state that is currently checked out.
>
> Isn't the natural conclusion that follows these two stentences
> "therefore, the latter is a very good place to use that helper
> function, too"?
Yeah, I did not use the helper function in builtin/checkout.c. Hence the "However". But I agree on the point of exporting the function. Therefore I have attached the patch with the updated message below.
Show 11 quoted lines
> Side note: the "@" is already problematic not just because
> "git branch @" would not refuse to create "refs/heads/@",
> but there is no ref "@" (like $GIT_DIR/refs/@ or $GIT_DIR/@)
> when it is used as a synonym for "HEAD". There is a check
> in builtin/checkout.c:update_refs_for_switch() that runs
> strcmp() on a token given by the end-user from the command
> line with "HEAD" to notice the no-op case "git checkout
> HEAD" but the code does not trigger when "@" is given, and
> it happens to work by accident. I really wish we didn't add
> that oddball synonym, but that is water under the bridge by
> now.
well, I suppose it is maybe annoying from the development perspective, but users seem to like the concept of it[1].
Show 9 quoted lines
> In any case, I think we'd find more places that currently treats the
> token "HEAD" given directly by the end-user specially and may want
> to teach at least some of them to also accept "@" the same way, and
> the helper function you are introducing may become useful in the
> future, at which time we may move it to a more public header. If it
> needs to be shared already between add-patch.c and builtin/checkout.c
> (I am guessing what you meant with "However" as an excuse for open
> coding it instead of sharing the code), perhaps we should do so without
> waiting for that future, though. I dunno.
Yeah, that "However" was for not using the helper function.
> If we choose to do so, for now, a squashable patch may look like the
> attached, but we'd need to update the log message while squashing it
> in.
Thanks for the patch. Updated message is below.
[Footnote] [1]: https://www.reddit.com/r/git/comments/k15cqm/do_you_know_is_a_shortcut_for_head/
-- >8 --
Subject: [PATCH] add-patch: classify '@' as a synonym for 'HEAD'
Currently, (checkout, reset, restore) commands correctly take '@' as a synonym for 'HEAD'. However, in patch mode (-p/--patch), for both '@' and 'HEAD', different prompts/messages are given by the commands mentioned above (because of applying reverse mode(-R) in case of '@'). This is due to the literal and only string comparison with the word 'HEAD' in run_add_p(). Synonymity between '@' and 'HEAD' is obviously desired, especially since '@' already resolves to 'HEAD'.
Therefore, make a new function the_user_meant_head() which takes the revision string and compares it to 'HEAD' as well as '@'. Also in builtin/checkout.c, there is a logic to convert all command line input rev to the raw object name for underlying machinery (e.g., diff-index) that does not recognize the <a>...<b> notation, but we'd need to leave 'HEAD' intact. Now we need to teach that '@' is a synonym to 'HEAD' to that code and leave '@' intact, too. Therefore, this function is already useful in add-patch.c and builtin/checkout.c and may also become helpful in other places in future. Therefore, it makes sense to export it.
There is one unintended side-effect/behavior change of this, even if there exists a branch named '@', when providing '@' as a rev-source to (checkout, reset, restore) commands in patch mode, it will consider it as HEAD. This is due to the behavior of diff-index. However, naming a branch '@' is an obvious foot-gun and there are many existing commands which already take '@' for 'HEAD' regardless of whether 'refs/heads/@' exists or not (e.g., 'git log @', 'git push origin @' etc.). Therefore, this should be fine.
Also, add tests for checking the above mentioned synonymity.
Co-authored-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Ghanshyam Thakkar <shyamthakkar001@gmail.com>
---
add-interactive.h | 14 ++++++++++++
add-patch.c | 6 ++---
builtin/checkout.c | 10 ++++-----
t/t2016-checkout-patch.sh | 46 ++++++++++++++++++++++-----------------
t/t2071-restore-patch.sh | 18 +++++++++------
t/t7105-reset-patch.sh | 10 +++++++++
6 files changed, 69 insertions(+), 35 deletions(-)
Show changes to 6 files +69 −35
add-interactive.h, add-patch.c, builtin/checkout.c, t/t2016-checkout-patch.sh, t/t2071-restore-patch.sh, t/t7105-reset-patch.sh
diff --git a/add-interactive.h b/add-interactive.h
index 693f125e8e..ca7326336d 100644
--- a/add-interactive.h
+++ b/add-interactive.h
@@ -38,4 +38,18 @@ enum add_p_mode {
int run_add_p(struct repository *r, enum add_p_mode mode,
const char *revision, const struct pathspec *ps);
+/*
+ * When the user gives these tokens from the command line, they mean
+ * the state that the currently checked out state came from. This
+ * single bit of information affects the direction in which the patch
+ * is presented to the end-user: are we showing a patch to go back to
+ * the currently committed state, or are we showing a patch to move
+ * forward to the given commit that may be different from the
+ * committed state we started with?
+ */
+static inline int the_user_meant_head(const char *rev)
+{
+ return !strcmp(rev, "HEAD") || !strcmp(rev, "@");
+}
+
#endif
diff --git a/add-patch.c b/add-patch.c
index 68f525b35c..5502acebb8 100644
--- a/add-patch.c
+++ b/add-patch.c
@@ -1729,21 +1729,21 @@ int run_add_p(struct repository *r, enum add_p_mode mode,
if (mode == ADD_P_STASH)
s.mode = &patch_mode_stash;
else if (mode == ADD_P_RESET) {
- if (!revision || !strcmp(revision, "HEAD"))
+ if (!revision || the_user_meant_head(revision))
s.mode = &patch_mode_reset_head;
else
s.mode = &patch_mode_reset_nothead;
} else if (mode == ADD_P_CHECKOUT) {
if (!revision)
s.mode = &patch_mode_checkout_index;
- else if (!strcmp(revision, "HEAD"))
+ else if (the_user_meant_head(revision))
s.mode = &patch_mode_checkout_head;
else
s.mode = &patch_mode_checkout_nothead;
} else if (mode == ADD_P_WORKTREE) {
if (!revision)
s.mode = &patch_mode_checkout_index;
- else if (!strcmp(revision, "HEAD"))
+ else if (the_user_meant_head(revision))
s.mode = &patch_mode_worktree_head;
else
s.mode = &patch_mode_worktree_nothead;
diff --git a/builtin/checkout.c b/builtin/checkout.c
index a6e30931b5..63c669b157 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -539,12 +539,12 @@ static int checkout_paths(const struct checkout_opts *opts,
* recognized by diff-index), we will always replace the name
* with the hex of the commit (whether it's in `...` form or
* not) for the run_add_interactive() machinery to work
- * properly. However, there is special logic for the HEAD case
- * so we mustn't replace that. Also, when we were given a
- * tree-object, new_branch_info->commit would be NULL, but we
- * do not have to do any replacement, either.
+ * properly. However, there is special logic for the 'HEAD' and
+ * '@' case so we mustn't replace that. Also, when we were
+ * given a tree-object, new_branch_info->commit would be NULL,
+ * but we do not have to do any replacement, either.
*/
- if (rev && new_branch_info->commit && strcmp(rev, "HEAD"))
+ if (rev && new_branch_info->commit && !the_user_meant_head(rev))
rev = oid_to_hex_r(rev_oid, &new_branch_info->commit->object.oid);
if (opts->checkout_index && opts->checkout_worktree)
diff --git a/t/t2016-checkout-patch.sh b/t/t2016-checkout-patch.sh
index 747eb5563e..c4f9bf09aa 100755
--- a/t/t2016-checkout-patch.sh
+++ b/t/t2016-checkout-patch.sh
@@ -38,26 +38,32 @@ test_expect_success 'git checkout -p with staged changes' '
verify_state dir/foo index index
'
-test_expect_success 'git checkout -p HEAD with NO staged changes: abort' '
- set_and_save_state dir/foo work head &&
- test_write_lines n y n | git checkout -p HEAD &&
- verify_saved_state bar &&
- verify_saved_state dir/foo
-'
-
-test_expect_success 'git checkout -p HEAD with NO staged changes: apply' '
- test_write_lines n y y | git checkout -p HEAD &&
- verify_saved_state bar &&
- verify_state dir/foo head head
-'
-
-test_expect_success 'git checkout -p HEAD with change already staged' '
- set_state dir/foo index index &&
- # the third n is to get out in case it mistakenly does not apply
- test_write_lines n y n | git checkout -p HEAD &&
- verify_saved_state bar &&
- verify_state dir/foo head head
-'
+for opt in "HEAD" "@"
+do
+ test_expect_success "git checkout -p $opt with NO staged changes: abort" '
+ set_and_save_state dir/foo work head &&
+ test_write_lines n y n | git checkout -p $opt >output &&
+ verify_saved_state bar &&
+ verify_saved_state dir/foo &&
+ test_grep "Discard" output
+ '
+
+ test_expect_success "git checkout -p $opt with NO staged changes: apply" '
+ test_write_lines n y y | git checkout -p $opt >output &&
+ verify_saved_state bar &&
+ verify_state dir/foo head head &&
+ test_grep "Discard" output
+ '
+
+ test_expect_success "git checkout -p $opt with change already staged" '
+ set_state dir/foo index index &&
+ # the third n is to get out in case it mistakenly does not apply
+ test_write_lines n y n | git checkout -p $opt >output &&
+ verify_saved_state bar &&
+ verify_state dir/foo head head &&
+ test_grep "Discard" output
+ '
+done
test_expect_success 'git checkout -p HEAD^...' '
# the third n is to get out in case it mistakenly does not apply
diff --git a/t/t2071-restore-patch.sh b/t/t2071-restore-patch.sh
index b5c5c0ff7e..3dc9184b4a 100755
--- a/t/t2071-restore-patch.sh
+++ b/t/t2071-restore-patch.sh
@@ -44,13 +44,17 @@ test_expect_success PERL 'git restore -p with staged changes' '
verify_state dir/foo index index
'
-test_expect_success PERL 'git restore -p --source=HEAD' '
- set_state dir/foo work index &&
- # the third n is to get out in case it mistakenly does not apply
- test_write_lines n y n | git restore -p --source=HEAD &&
- verify_saved_state bar &&
- verify_state dir/foo head index
-'
+for opt in "HEAD" "@"
+do
+ test_expect_success PERL "git restore -p --source=$opt" '
+ set_state dir/foo work index &&
+ # the third n is to get out in case it mistakenly does not apply
+ test_write_lines n y n | git restore -p --source=$opt >output &&
+ verify_saved_state bar &&
+ verify_state dir/foo head index &&
+ test_grep "Discard" output
+ '
+done
test_expect_success PERL 'git restore -p --source=HEAD^' '
set_state dir/foo work index &&
diff --git a/t/t7105-reset-patch.sh b/t/t7105-reset-patch.sh
index 05079c7246..ec7f16dfb6 100755
--- a/t/t7105-reset-patch.sh
+++ b/t/t7105-reset-patch.sh
@@ -33,6 +33,16 @@ test_expect_success PERL 'git reset -p' '
test_grep "Unstage" output
'
+for opt in "HEAD" "@"
+do
+ test_expect_success PERL "git reset -p $opt" '
+ test_write_lines n y | git reset -p $opt >output &&
+ verify_state dir/foo work head &&
+ verify_saved_state bar &&
+ test_grep "Unstage" output
+ '
+done
+
test_expect_success PERL 'git reset -p HEAD^' '
test_write_lines n y | git reset -p HEAD^ >output &&
verify_state dir/foo work parent &&
--
2.43.0
Ghanshyam Thakkar
