Teach 'git-apply --whitespace=strip' to remove empty lines at end of file

---
 builtin-apply.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

index 0399743..f17f838 100644
@@ -1738,6 +1738,10 @@ static int apply_one_fragment(struct buffer_desc *desc, struct fragment *frag, i
 		newsize--;
 	}
 
+	if (new_whitespace == strip_whitespace)
+		while (newsize > 1 && !strncmp(new + newsize - 2, "\n\n", 2))
+			newsize--;
+
 	oldlines = old;
 	newlines = new;
 	leading = frag->leading;

1.5.2.rc3.87.g404fd-dirty

What about this?

builtin-apply.c | 13 +++++++++----

1 files changed, 9 insertions(+), 4 deletions(-)

index 9e82757..113c71f 100644
@@ -1746,10 +1746,15 @@ static int apply_one_fragment(struct

buffer_desc *desc, struct fragment *frag, i

		newsize--;
	}

- if (new_whitespace == strip_whitespace)
- while (newsize > 1 && !strncmp(new + newsize - 2, "\n\n", 2))
- newsize--;
-
+ if (new_whitespace == strip_whitespace) {
+ int cnt1 = 1, cnt2 = 1;
+ while (newsize - cnt1 > 1 && new[newsize - cnt1] == '\n')
+ cnt1++;
+ while (oldsize - cnt2 > 1 && new[newsize - cnt2] == '\n')
+ cnt2++;
+ if (cnt1 > cnt2 && cnt1 > 2)
+ newsize -= cnt1 - cnt2;
+ }

	oldlines = old;
	newlines = new;
	leading = frag->leading;

You count the trailing blank lines in new and old, and if new one has more you strip them out, which _sounds_ sane.

But it is unclear to me how you are limiting the processing to the very end of the file. The "new" and "old" essentially is a patch fragment that is separated into two, and the part you modified with your patch does not know if the hunk applies at the end of the patch yet.

That is, given this patch:

index 9e82757..113c71f 100644
@@ -1746,10 +1746,15 @@ static int apply_one_fragment(struct buffer_desc *des..
                newsize--;
        }
 
-       if (new_whitespace == strip_whitespace)
-               while (newsize > 1 && !strncmp(new + newsize - 2, "\n\n", 2))
-                       newsize--;
-
+       if (new_whitespace == strip_whitespace) {
+               int cnt1 =  1, cnt2 = 1;
+               while (newsize -  cnt1 > 1 && new[newsize - cnt1] == '\n')
+                       cnt1++;
+               while (oldsize -  cnt2 > 1 && new[newsize - cnt2] == '\n')
+                       cnt2++;
+               if (cnt1 > cnt2 && cnt1 > 2)
+                       newsize -= cnt1 - cnt2;
+       }
        oldlines = old;
        newlines = new;
        leading = frag->leading;

"new" has these lines

                newsize--;
        }

        if (new_whitespace == strip_whitespace) {
                int cnt1 =  1, cnt2 = 1;
                while (newsize -  cnt1 > 1 && new[newsize - cnt1] == '\n')
                        cnt1++;
                while (oldsize -  cnt2 > 1 && new[newsize - cnt2] == '\n')
                        cnt2++;
                if (cnt1 > cnt2 && cnt1 > 2)
                        newsize -= cnt1 - cnt2;
        }
        oldlines = old;
        newlines = new;
        leading = frag->leading;

while "old" has this:

                newsize--;
        }

        if (new_whitespace == strip_whitespace)
                while (newsize > 1 && !strncmp(new + newsize - 2, "\n\n", 2))
                        newsize--;

        oldlines = old;
        newlines = new;
        leading = frag->leading;

and these may or may not be at the end of the file, so inspecting what blank lines they have at the end is not sufficient. If "new" does not introduce new blank lines at its end, then you can be sure that you are not adding trailing blank lines, but even if "new" does introduce a new blank line at the end, you do not know if that is adding it to the end of the file, or in the middle.

You do not know where the hunk is applied until you do the loop that follows the part your patch we are discussing.

If I were doing this, I would probably do it this way:

(1) Inside apply_one_fragment(), where "case '+':" appears, count the blank (not just '\n', but matches /^\s*$/) lines at the end of "new" side. As soon as you fall into "case ' ':" or "case '-':" or non-blank line in "case '+':", you reset the counter to zero, so that what you are counting is the number of blank lines that would have get added, if the hunk were to be applied at the end of the file. Keep that number ofter you separated the fragment into new and old.

(2) In the same function, inside the big "for (;;)" loop that figures out where to apply that "old" => "new" change, use the number you gathered in the step (1) to trim what is applied, where the real application happens, which is the part that has memmove()/memcpy(), only when you know you are applying the hunk at the end of the file. That is the only place in the function that knows where the hunk is being applied.