Support fuzzy patch

[uilianries]

fixes #5

Should close conan-io/conan#5963 too

[jgsogo]

I see your fix here and, although I've tried to, I cannot make a patch file that would break your implementation.

---

I have one consideration about this. If I use the patch file (see the non-matching line `YYYY')....

diff --git a/Jamroot b/Jamroot
index a6981dd..0c08f09 100644
--- a/Jamroot
+++ b/Jamroot
@@ -1,3 +1,4 @@
 X
 YYYY
+V
 Z

... IMO it is also a fuzzy patch and should behave the same. I see that the library, for this use case, returns an error from the # validate before patching section. Should we add the logic to the validation and fail? Is there any reason why it allows a fuzzy patch after the changed section but not before?

[uilianries]

I see. I think it's because the hunk @@ -1,3 +1,4 @@

The original file starts at line 1 and is 3 lines size. The initial validation didn't detect the my patch because it only checked the first 3 lines, ignoring Z.
In your case, YYYY comes into the original hunk.

We need to change the patch applying, but also the initial validation. The question is, should we add an option to allow fuzzy patch? We are breakingthe original behavior with this patch.

[jgsogo]

From my point of view:

1. FIX: a fuzzy-patch after the actual changes in the patch-file should fail (as it is failing if the fuzzy is before the actual changes). If we had had this behavior before, the issue with boost wouldn't have happened.
2. FEATURE: add an argument/option to allow fuzzy patches. But this feature could wait.

[uilianries]

Fair enough! I'll check the bug again. Thanks for reporting this new case.

[jgsogo]

If we accept fuzzy patches, it should we as an opt-in (using an option), by default it is safer for us to fail

[jgsogo]

Great! Thanks a lot, @uilianries

I know there are lots of use-cases to test, but I agree we should go step by step and assume that everything is working if anyone has reported it... (my head is thinking about patches removing lines, patches substituting one line by another, adding more than one line, removing several,... 🔬 😅 ).

[uilianries]

@jgsogo Thanks for reviewing!! 💪

[lasote]

Released patch-ng==1.17.2

[uilianries]

thanks! I gonna restart that PR in Conan