[PATCH 0/2] add p in C tweaks

[PATCH 0/2] add p in C tweaks

[Phillip Wood via GitGitGadget]

A code cleanup and small bug fix for the C version of add -p

dscho has pointed out that the bug fix in the second patch gets lost in the
other changes and suggested adding the last member of the enum (which fixes
the bug with handling 'e') as a separate patch. I'm unsure as it feels odd
to split up the introduction of the flags - I'd be interested to hear what
others think.

Phillip Wood (2):
  add -p: use ALLOC_GROW_BY instead of ALLOW_GROW
  add -p: fix checking of user input

 add-patch.c | 67 +++++++++++++++++++++++++++++++++--------------------
 1 file changed, 42 insertions(+), 25 deletions(-)


base-commit: 47ae905ffb98cc4d4fd90083da6bc8dab55d9ecc
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-702%2Fphillipwood%2Fwip%2Fadd-p-fixes-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-702/phillipwood/wip/add-p-fixes-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/702
-- 
gitgitgadget

[PATCH 1/2] add -p: use ALLOC_GROW_BY instead of ALLOW_GROW

[Phillip Wood via GitGitGadget]

From: Phillip Wood <phillip.wood@dunelm.org.uk>

This simplifies the code slightly, especially the third case where
hunk_nr was incremented a few lines before ALLOC_GROW().

Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
---
 add-patch.c | 13 ++++---------
 1 file changed, 4 insertions(+), 9 deletions(-)

diff --git a/add-patch.c b/add-patch.c
index f899389e2c..a15fa407be 100644
--- a/add-patch.c
+++ b/add-patch.c
@@ -457,11 +457,9 @@ static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
 			eol = pend;
 
 		if (starts_with(p, "diff ")) {
-			s->file_diff_nr++;
-			ALLOC_GROW(s->file_diff, s->file_diff_nr,
+			ALLOC_GROW_BY(s->file_diff, s->file_diff_nr, 1,
 				   file_diff_alloc);
 			file_diff = s->file_diff + s->file_diff_nr - 1;
-			memset(file_diff, 0, sizeof(*file_diff));
 			hunk = &file_diff->head;
 			hunk->start = p - plain->buf;
 			if (colored_p)
@@ -483,11 +481,9 @@ static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
 				 */
 				hunk->splittable_into++;
 
-			file_diff->hunk_nr++;
-			ALLOC_GROW(file_diff->hunk, file_diff->hunk_nr,
+			ALLOC_GROW_BY(file_diff->hunk, file_diff->hunk_nr, 1,
 				   file_diff->hunk_alloc);
 			hunk = file_diff->hunk + file_diff->hunk_nr - 1;
-			memset(hunk, 0, sizeof(*hunk));
 
 			hunk->start = p - plain->buf;
 			if (colored)
@@ -511,7 +507,7 @@ static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
 			if (file_diff->mode_change)
 				BUG("double mode change?\n\n%.*s",
 				    (int)(eol - plain->buf), plain->buf);
-			if (file_diff->hunk_nr++)
+			if (file_diff->hunk_nr)
 				BUG("mode change in the middle?\n\n%.*s",
 				    (int)(eol - plain->buf), plain->buf);
 
@@ -520,9 +516,8 @@ static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
 			 * is _part of_ the header "hunk".
 			 */
 			file_diff->mode_change = 1;
-			ALLOC_GROW(file_diff->hunk, file_diff->hunk_nr,
+			ALLOC_GROW_BY(file_diff->hunk, file_diff->hunk_nr, 1,
 				   file_diff->hunk_alloc);
-			memset(file_diff->hunk, 0, sizeof(struct hunk));
 			file_diff->hunk->start = p - plain->buf;
 			if (colored_p)
 				file_diff->hunk->colored_start =
-- 
gitgitgadget

[PATCH 2/2] add -p: fix checking of user input

[Phillip Wood via GitGitGadget]

From: Phillip Wood <phillip.wood@dunelm.org.uk>

When a file has been deleted the C version of add -p allows the user
to edit a hunk even though 'e' is not in the list of allowed
responses. (I think 'e' is disallowed because if the file is edited it
is no longer a deletion and we're not set up to rewrite the diff
header).

The invalid response was allowed because the test that determines
whether to display 'e' was not duplicated correctly in the code that
processes the user's choice. Fix this by using flags that are set when
constructing the prompt and checked when processing the user's choice
rather than repeating the check itself.

Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
---
 add-patch.c | 54 +++++++++++++++++++++++++++++++++++++----------------
 1 file changed, 38 insertions(+), 16 deletions(-)

diff --git a/add-patch.c b/add-patch.c
index a15fa407be..907c05b3c1 100644
--- a/add-patch.c
+++ b/add-patch.c
@@ -1352,6 +1352,15 @@ static int patch_update_file(struct add_p_state *s,
 	struct child_process cp = CHILD_PROCESS_INIT;
 	int colored = !!s->colored.len, quit = 0;
 	enum prompt_mode_type prompt_mode_type;
+	enum {
+		ALLOW_GOTO_PREVIOUS_HUNK = 1 << 0,
+		ALLOW_GOTO_PREVIOUS_UNDECIDED_HUNK = 1 << 1,
+		ALLOW_GOTO_NEXT_HUNK = 1 << 2,
+		ALLOW_GOTO_NEXT_UNDECIDED_HUNK = 1 << 3,
+		ALLOW_SEARCH_AND_GOTO = 1 << 4,
+		ALLOW_SPLIT = 1 << 5,
+		ALLOW_EDIT = 1 << 6
+	} permitted = 0;
 
 	if (!file_diff->hunk_nr)
 		return 0;
@@ -1388,22 +1397,35 @@ static int patch_update_file(struct add_p_state *s,
 		fputs(s->buf.buf, stdout);
 
 		strbuf_reset(&s->buf);
-		if (undecided_previous >= 0)
+		if (undecided_previous >= 0) {
+			permitted |= ALLOW_GOTO_PREVIOUS_UNDECIDED_HUNK;
 			strbuf_addstr(&s->buf, ",k");
-		if (hunk_index)
+		}
+		if (hunk_index) {
+			permitted |= ALLOW_GOTO_PREVIOUS_HUNK;
 			strbuf_addstr(&s->buf, ",K");
-		if (undecided_next >= 0)
+		}
+		if (undecided_next >= 0) {
+			permitted |= ALLOW_GOTO_NEXT_UNDECIDED_HUNK;
 			strbuf_addstr(&s->buf, ",j");
-		if (hunk_index + 1 < file_diff->hunk_nr)
+		}
+		if (hunk_index + 1 < file_diff->hunk_nr) {
+			permitted |= ALLOW_GOTO_NEXT_HUNK;
 			strbuf_addstr(&s->buf, ",J");
-		if (file_diff->hunk_nr > 1)
+		}
+		if (file_diff->hunk_nr > 1) {
+			permitted |= ALLOW_SEARCH_AND_GOTO;
 			strbuf_addstr(&s->buf, ",g,/");
-		if (hunk->splittable_into > 1)
+		}
+		if (hunk->splittable_into > 1) {
+			permitted |= ALLOW_SPLIT;
 			strbuf_addstr(&s->buf, ",s");
+		}
 		if (hunk_index + 1 > file_diff->mode_change &&
-		    !file_diff->deleted)
+		    !file_diff->deleted) {
+			permitted |= ALLOW_EDIT;
 			strbuf_addstr(&s->buf, ",e");
-
+		}
 		if (file_diff->deleted)
 			prompt_mode_type = PROMPT_DELETION;
 		else if (file_diff->added)
@@ -1452,22 +1474,22 @@ static int patch_update_file(struct add_p_state *s,
 				break;
 			}
 		} else if (s->answer.buf[0] == 'K') {
-			if (hunk_index)
+			if (permitted & ALLOW_GOTO_PREVIOUS_HUNK)
 				hunk_index--;
 			else
 				err(s, _("No previous hunk"));
 		} else if (s->answer.buf[0] == 'J') {
-			if (hunk_index + 1 < file_diff->hunk_nr)
+			if (permitted & ALLOW_GOTO_NEXT_HUNK)
 				hunk_index++;
 			else
 				err(s, _("No next hunk"));
 		} else if (s->answer.buf[0] == 'k') {
-			if (undecided_previous >= 0)
+			if (permitted & ALLOW_GOTO_PREVIOUS_UNDECIDED_HUNK)
 				hunk_index = undecided_previous;
 			else
 				err(s, _("No previous hunk"));
 		} else if (s->answer.buf[0] == 'j') {
-			if (undecided_next >= 0)
+			if (permitted & ALLOW_GOTO_NEXT_UNDECIDED_HUNK)
 				hunk_index = undecided_next;
 			else
 				err(s, _("No next hunk"));
@@ -1475,7 +1497,7 @@ static int patch_update_file(struct add_p_state *s,
 			char *pend;
 			unsigned long response;
 
-			if (file_diff->hunk_nr < 2) {
+			if (!(permitted & ALLOW_SEARCH_AND_GOTO)) {
 				err(s, _("No other hunks to goto"));
 				continue;
 			}
@@ -1512,7 +1534,7 @@ static int patch_update_file(struct add_p_state *s,
 			regex_t regex;
 			int ret;
 
-			if (file_diff->hunk_nr < 2) {
+			if (!(permitted & ALLOW_SEARCH_AND_GOTO)) {
 				err(s, _("No other hunks to search"));
 				continue;
 			}
@@ -1557,7 +1579,7 @@ static int patch_update_file(struct add_p_state *s,
 			hunk_index = i;
 		} else if (s->answer.buf[0] == 's') {
 			size_t splittable_into = hunk->splittable_into;
-			if (splittable_into < 2)
+			if (!(permitted & ALLOW_SPLIT))
 				err(s, _("Sorry, cannot split this hunk"));
 			else if (!split_hunk(s, file_diff,
 					     hunk - file_diff->hunk))
@@ -1565,7 +1587,7 @@ static int patch_update_file(struct add_p_state *s,
 						 _("Split into %d hunks."),
 						 (int)splittable_into);
 		} else if (s->answer.buf[0] == 'e') {
-			if (hunk_index + 1 == file_diff->mode_change)
+			if (!(permitted & ALLOW_EDIT))
 				err(s, _("Sorry, cannot edit this hunk"));
 			else if (edit_hunk_loop(s, file_diff, hunk) >= 0) {
 				hunk->use = USE_HUNK;
-- 
gitgitgadget

Re: [PATCH 1/2] add -p: use ALLOC_GROW_BY instead of ALLOW_GROW

[Junio C Hamano]

"Phillip Wood via GitGitGadget" <gitgitgadget@gmail.com> writes:

> From: Phillip Wood <phillip.wood@dunelm.org.uk>
>
> This simplifies the code slightly, especially the third case where
> hunk_nr was incremented a few lines before ALLOC_GROW().

OK, we lose memset()s that appear to be separate but is a part of
adding more elements.  Makes sense.

>
> Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
> ---
>  add-patch.c | 13 ++++---------
>  1 file changed, 4 insertions(+), 9 deletions(-)
>
> diff --git a/add-patch.c b/add-patch.c
> index f899389e2c..a15fa407be 100644
> --- a/add-patch.c
> +++ b/add-patch.c
> @@ -457,11 +457,9 @@ static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
>  			eol = pend;
>  
>  		if (starts_with(p, "diff ")) {
> -			s->file_diff_nr++;
> -			ALLOC_GROW(s->file_diff, s->file_diff_nr,
> +			ALLOC_GROW_BY(s->file_diff, s->file_diff_nr, 1,
>  				   file_diff_alloc);
>  			file_diff = s->file_diff + s->file_diff_nr - 1;
> -			memset(file_diff, 0, sizeof(*file_diff));
>  			hunk = &file_diff->head;
>  			hunk->start = p - plain->buf;
>  			if (colored_p)
> @@ -483,11 +481,9 @@ static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
>  				 */
>  				hunk->splittable_into++;
>  
> -			file_diff->hunk_nr++;
> -			ALLOC_GROW(file_diff->hunk, file_diff->hunk_nr,
> +			ALLOC_GROW_BY(file_diff->hunk, file_diff->hunk_nr, 1,
>  				   file_diff->hunk_alloc);
>  			hunk = file_diff->hunk + file_diff->hunk_nr - 1;
> -			memset(hunk, 0, sizeof(*hunk));
>  
>  			hunk->start = p - plain->buf;
>  			if (colored)
> @@ -511,7 +507,7 @@ static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
>  			if (file_diff->mode_change)
>  				BUG("double mode change?\n\n%.*s",
>  				    (int)(eol - plain->buf), plain->buf);
> -			if (file_diff->hunk_nr++)
> +			if (file_diff->hunk_nr)
>  				BUG("mode change in the middle?\n\n%.*s",
>  				    (int)(eol - plain->buf), plain->buf);
>  
> @@ -520,9 +516,8 @@ static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
>  			 * is _part of_ the header "hunk".
>  			 */
>  			file_diff->mode_change = 1;
> -			ALLOC_GROW(file_diff->hunk, file_diff->hunk_nr,
> +			ALLOC_GROW_BY(file_diff->hunk, file_diff->hunk_nr, 1,
>  				   file_diff->hunk_alloc);
> -			memset(file_diff->hunk, 0, sizeof(struct hunk));
>  			file_diff->hunk->start = p - plain->buf;
>  			if (colored_p)
>  				file_diff->hunk->colored_start =

Re: [PATCH 2/2] add -p: fix checking of user input

[Johannes Schindelin]

Hi Phillip,

On Mon, 17 Aug 2020, Phillip Wood via GitGitGadget wrote:

> From: Phillip Wood <phillip.wood@dunelm.org.uk>
>
> When a file has been deleted the C version of add -p allows the user
> to edit a hunk even though 'e' is not in the list of allowed
> responses. (I think 'e' is disallowed because if the file is edited it
> is no longer a deletion and we're not set up to rewrite the diff
> header).
>
> The invalid response was allowed because the test that determines
> whether to display 'e' was not duplicated correctly in the code that
> processes the user's choice. Fix this by using flags that are set when
> constructing the prompt and checked when processing the user's choice
> rather than repeating the check itself.
>
> Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>

As I had mentioned on the PR, I would much rather have a bug-for-bug
conversion to use the `enum`, and the fix for the `edit` case as a
separate patch on top.

Thank you,
Dscho

> ---
>  add-patch.c | 54 +++++++++++++++++++++++++++++++++++++----------------
>  1 file changed, 38 insertions(+), 16 deletions(-)
>
> diff --git a/add-patch.c b/add-patch.c
> index a15fa407be..907c05b3c1 100644
> --- a/add-patch.c
> +++ b/add-patch.c
> @@ -1352,6 +1352,15 @@ static int patch_update_file(struct add_p_state *s,
>  	struct child_process cp = CHILD_PROCESS_INIT;
>  	int colored = !!s->colored.len, quit = 0;
>  	enum prompt_mode_type prompt_mode_type;
> +	enum {
> +		ALLOW_GOTO_PREVIOUS_HUNK = 1 << 0,
> +		ALLOW_GOTO_PREVIOUS_UNDECIDED_HUNK = 1 << 1,
> +		ALLOW_GOTO_NEXT_HUNK = 1 << 2,
> +		ALLOW_GOTO_NEXT_UNDECIDED_HUNK = 1 << 3,
> +		ALLOW_SEARCH_AND_GOTO = 1 << 4,
> +		ALLOW_SPLIT = 1 << 5,
> +		ALLOW_EDIT = 1 << 6
> +	} permitted = 0;
>
>  	if (!file_diff->hunk_nr)
>  		return 0;
> @@ -1388,22 +1397,35 @@ static int patch_update_file(struct add_p_state *s,
>  		fputs(s->buf.buf, stdout);
>
>  		strbuf_reset(&s->buf);
> -		if (undecided_previous >= 0)
> +		if (undecided_previous >= 0) {
> +			permitted |= ALLOW_GOTO_PREVIOUS_UNDECIDED_HUNK;
>  			strbuf_addstr(&s->buf, ",k");
> -		if (hunk_index)
> +		}
> +		if (hunk_index) {
> +			permitted |= ALLOW_GOTO_PREVIOUS_HUNK;
>  			strbuf_addstr(&s->buf, ",K");
> -		if (undecided_next >= 0)
> +		}
> +		if (undecided_next >= 0) {
> +			permitted |= ALLOW_GOTO_NEXT_UNDECIDED_HUNK;
>  			strbuf_addstr(&s->buf, ",j");
> -		if (hunk_index + 1 < file_diff->hunk_nr)
> +		}
> +		if (hunk_index + 1 < file_diff->hunk_nr) {
> +			permitted |= ALLOW_GOTO_NEXT_HUNK;
>  			strbuf_addstr(&s->buf, ",J");
> -		if (file_diff->hunk_nr > 1)
> +		}
> +		if (file_diff->hunk_nr > 1) {
> +			permitted |= ALLOW_SEARCH_AND_GOTO;
>  			strbuf_addstr(&s->buf, ",g,/");
> -		if (hunk->splittable_into > 1)
> +		}
> +		if (hunk->splittable_into > 1) {
> +			permitted |= ALLOW_SPLIT;
>  			strbuf_addstr(&s->buf, ",s");
> +		}
>  		if (hunk_index + 1 > file_diff->mode_change &&
> -		    !file_diff->deleted)
> +		    !file_diff->deleted) {
> +			permitted |= ALLOW_EDIT;
>  			strbuf_addstr(&s->buf, ",e");
> -
> +		}
>  		if (file_diff->deleted)
>  			prompt_mode_type = PROMPT_DELETION;
>  		else if (file_diff->added)
> @@ -1452,22 +1474,22 @@ static int patch_update_file(struct add_p_state *s,
>  				break;
>  			}
>  		} else if (s->answer.buf[0] == 'K') {
> -			if (hunk_index)
> +			if (permitted & ALLOW_GOTO_PREVIOUS_HUNK)
>  				hunk_index--;
>  			else
>  				err(s, _("No previous hunk"));
>  		} else if (s->answer.buf[0] == 'J') {
> -			if (hunk_index + 1 < file_diff->hunk_nr)
> +			if (permitted & ALLOW_GOTO_NEXT_HUNK)
>  				hunk_index++;
>  			else
>  				err(s, _("No next hunk"));
>  		} else if (s->answer.buf[0] == 'k') {
> -			if (undecided_previous >= 0)
> +			if (permitted & ALLOW_GOTO_PREVIOUS_UNDECIDED_HUNK)
>  				hunk_index = undecided_previous;
>  			else
>  				err(s, _("No previous hunk"));
>  		} else if (s->answer.buf[0] == 'j') {
> -			if (undecided_next >= 0)
> +			if (permitted & ALLOW_GOTO_NEXT_UNDECIDED_HUNK)
>  				hunk_index = undecided_next;
>  			else
>  				err(s, _("No next hunk"));
> @@ -1475,7 +1497,7 @@ static int patch_update_file(struct add_p_state *s,
>  			char *pend;
>  			unsigned long response;
>
> -			if (file_diff->hunk_nr < 2) {
> +			if (!(permitted & ALLOW_SEARCH_AND_GOTO)) {
>  				err(s, _("No other hunks to goto"));
>  				continue;
>  			}
> @@ -1512,7 +1534,7 @@ static int patch_update_file(struct add_p_state *s,
>  			regex_t regex;
>  			int ret;
>
> -			if (file_diff->hunk_nr < 2) {
> +			if (!(permitted & ALLOW_SEARCH_AND_GOTO)) {
>  				err(s, _("No other hunks to search"));
>  				continue;
>  			}
> @@ -1557,7 +1579,7 @@ static int patch_update_file(struct add_p_state *s,
>  			hunk_index = i;
>  		} else if (s->answer.buf[0] == 's') {
>  			size_t splittable_into = hunk->splittable_into;
> -			if (splittable_into < 2)
> +			if (!(permitted & ALLOW_SPLIT))
>  				err(s, _("Sorry, cannot split this hunk"));
>  			else if (!split_hunk(s, file_diff,
>  					     hunk - file_diff->hunk))
> @@ -1565,7 +1587,7 @@ static int patch_update_file(struct add_p_state *s,
>  						 _("Split into %d hunks."),
>  						 (int)splittable_into);
>  		} else if (s->answer.buf[0] == 'e') {
> -			if (hunk_index + 1 == file_diff->mode_change)
> +			if (!(permitted & ALLOW_EDIT))
>  				err(s, _("Sorry, cannot edit this hunk"));
>  			else if (edit_hunk_loop(s, file_diff, hunk) >= 0) {
>  				hunk->use = USE_HUNK;
> --
> gitgitgadget
>

Re: [PATCH 0/2] add p in C tweaks

[Johannes Schindelin]

Hi Phillip,

On Mon, 17 Aug 2020, Phillip Wood via GitGitGadget wrote:

> A code cleanup and small bug fix for the C version of add -p
>
> dscho has pointed out that the bug fix in the second patch gets lost in the
> other changes and suggested adding the last member of the enum (which fixes
> the bug with handling 'e') as a separate patch. I'm unsure as it feels odd
> to split up the introduction of the flags - I'd be interested to hear what
> others think.

Yep, apart from this issue I am fine with the patches as-are.

Thanks,
Dscho

>
> Phillip Wood (2):
>   add -p: use ALLOC_GROW_BY instead of ALLOW_GROW
>   add -p: fix checking of user input
>
>  add-patch.c | 67 +++++++++++++++++++++++++++++++++--------------------
>  1 file changed, 42 insertions(+), 25 deletions(-)
>
>
> base-commit: 47ae905ffb98cc4d4fd90083da6bc8dab55d9ecc
> Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-702%2Fphillipwood%2Fwip%2Fadd-p-fixes-v1
> Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-702/phillipwood/wip/add-p-fixes-v1
> Pull-Request: https://github.com/gitgitgadget/git/pull/702
> --
> gitgitgadget
>

Re: [PATCH 0/2] add p in C tweaks

[Junio C Hamano]

"Phillip Wood via GitGitGadget" <gitgitgadget@gmail.com> writes:

> A code cleanup and small bug fix for the C version of add -p
>
> dscho has pointed out that the bug fix in the second patch gets lost in the
> other changes and suggested adding the last member of the enum (which fixes
> the bug with handling 'e') as a separate patch. I'm unsure as it feels odd
> to split up the introduction of the flags - I'd be interested to hear what
> others think.

Essentially, the original was doing:

    - In early part of patch_update_file(), decide what option to show
      in s->buf using "if (undecided_previous >= 0)" etc. boolean
      expression that is tailored for each command;

    - In later part of patch_update_file(), after getting an answer
      to the end user, try to use the same boolean expression that
      is tailored for each command to see if the given command is
      acceptable.

and the bug was that each pair of boolean expressions that are
supposed to be identical were duplicated in two places, and one pair
was not identical by mistake.

Your [2/2] fixes it by turning the above to

    - In early part of patch_update_file(), decide what option to show
      in s->buf using "if (undecided_previous >= 0)" etc. boolean
      expression that is tailored for each command, *AND* record the
      fact that the command is allowed in the permitted bitmask.

    - In later part of patch_update_file(), after getting an answer
      to the end user, consult the permitted bitmask computed
      earlier to see if the given command is acceptable.

Since there no longer is duplicated boolean expressions that are
supposed to be the same but different by a bug, once this conversion
is made, it is impossible to have the bug.  For that reason, I do
not think the suggested split makes much sense.

A much saner split, if we have to split this step into two, would be
to first fix the bug keeping the code structure of the original,
i.e. the later part guards the 'e' command with

	if (hunk_index + 1 == file_diff->mode_change)

but the earlier part also required !file_diff->deleted, i.e. the
condition should have been

	if (hunk_index + 1 > file_diff->mode_change && !file_diff->deleted)

So without introducing enum and permitted bitmask, you can fix the
bug in place, replacing the incorrect boolean condition in the later
part that guards the 'e' command with a corrected one.  That would
be a minimum fix that can become your new [2/2], whose theme is "to
fix the bug with minumum change".

On top of that, you can convert the function again to reach the
final shape that writes each boolean condition only once and records
the permitted commands in the bitmask.  That can be your new [3/2],
whose these is "to make it impossible to introduce the bug previous
step fixed".


> Phillip Wood (2):
>   add -p: use ALLOC_GROW_BY instead of ALLOW_GROW
>   add -p: fix checking of user input
>
>  add-patch.c | 67 +++++++++++++++++++++++++++++++++--------------------
>  1 file changed, 42 insertions(+), 25 deletions(-)
>
>
> base-commit: 47ae905ffb98cc4d4fd90083da6bc8dab55d9ecc
> Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-702%2Fphillipwood%2Fwip%2Fadd-p-fixes-v1
> Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-702/phillipwood/wip/add-p-fixes-v1
> Pull-Request: https://github.com/gitgitgadget/git/pull/702

Re: [PATCH 0/2] add p in C tweaks

[Phillip Wood]

On 18/08/2020 20:44, Junio C Hamano wrote:
> "Phillip Wood via GitGitGadget" <gitgitgadget@gmail.com> writes:
> 
>> A code cleanup and small bug fix for the C version of add -p
>>
>> dscho has pointed out that the bug fix in the second patch gets lost in the
>> other changes and suggested adding the last member of the enum (which fixes
>> the bug with handling 'e') as a separate patch. I'm unsure as it feels odd
>> to split up the introduction of the flags - I'd be interested to hear what
>> others think.
> 
> Essentially, the original was doing:
> 
>     - In early part of patch_update_file(), decide what option to show
>       in s->buf using "if (undecided_previous >= 0)" etc. boolean
>       expression that is tailored for each command;
> 
>     - In later part of patch_update_file(), after getting an answer
>       to the end user, try to use the same boolean expression that
>       is tailored for each command to see if the given command is
>       acceptable.
> 
> and the bug was that each pair of boolean expressions that are
> supposed to be identical were duplicated in two places, and one pair
> was not identical by mistake.
> 
> Your [2/2] fixes it by turning the above to
> 
>     - In early part of patch_update_file(), decide what option to show
>       in s->buf using "if (undecided_previous >= 0)" etc. boolean
>       expression that is tailored for each command, *AND* record the
>       fact that the command is allowed in the permitted bitmask.
> 
>     - In later part of patch_update_file(), after getting an answer
>       to the end user, consult the permitted bitmask computed
>       earlier to see if the given command is acceptable.
> 
> Since there no longer is duplicated boolean expressions that are
> supposed to be the same but different by a bug, once this conversion
> is made, it is impossible to have the bug.  For that reason, I do
> not think the suggested split makes much sense.
> 
> A much saner split, if we have to split this step into two, would be
> to first fix the bug keeping the code structure of the original,
> i.e. the later part guards the 'e' command with
> 
> 	if (hunk_index + 1 == file_diff->mode_change)
> 
> but the earlier part also required !file_diff->deleted, i.e. the
> condition should have been
> 
> 	if (hunk_index + 1 > file_diff->mode_change && !file_diff->deleted)
> 
> So without introducing enum and permitted bitmask, you can fix the
> bug in place, replacing the incorrect boolean condition in the later
> part that guards the 'e' command with a corrected one.  That would
> be a minimum fix that can become your new [2/2], whose theme is "to
> fix the bug with minumum change".
> 
> On top of that, you can convert the function again to reach the
> final shape that writes each boolean condition only once and records
> the permitted commands in the bitmask.  That can be your new [3/2],
> whose these is "to make it impossible to introduce the bug previous
> step fixed".

Thanks that makes much more sense to me

Best Wishes

Phillip

>> Phillip Wood (2):
>>   add -p: use ALLOC_GROW_BY instead of ALLOW_GROW
>>   add -p: fix checking of user input
>>
>>  add-patch.c | 67 +++++++++++++++++++++++++++++++++--------------------
>>  1 file changed, 42 insertions(+), 25 deletions(-)
>>
>>
>> base-commit: 47ae905ffb98cc4d4fd90083da6bc8dab55d9ecc
>> Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-702%2Fphillipwood%2Fwip%2Fadd-p-fixes-v1
>> Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-702/phillipwood/wip/add-p-fixes-v1
>> Pull-Request: https://github.com/gitgitgadget/git/pull/702