[Support] Create Patch for new file from buffer

[brandonio21]

Hello all,

I am working with the use case of creating diffs from buffers. Everything is going well as there is decent support for it, especially in the form of Blob.diff_to_buffer. The function works great when changing content and will soon work for deleting a file (In #741). However, I cannot figure out a proper way to add files using Blob.diff_to_buffer.

Do you guys have any suggestions? In libgit2, the proper way is to call git_diff_blob_to_buffer and set the Blob* argument to NULL. However, pygit2 does not have a static function to be able to do this. Do you guys have any suggestions? Here are things I can think of:

1. Create a special "Empty" blob object (or give it an exists property) that can be used to signify a nonexistent blob and then do diff_to_buffer on that.

2. Expose a static Patch.from_blob_to_buffer() which can then be called like Patch.from_blob_to_buffer(None, buf).

The other thing I can think of, which does not yet exist, is adding a Tree.diff_to_buffer()/Tree.diff_to_blob() to libgit2, which would solve this problem since the Tree would know whether the blob is being added or removed. (Of course, this would then have to be wrapped in pygit2)

Thoughts?

[jdavid]

Hi,

Solution 1 is already there, no?

>>> import pygit2
>>> r = pygit2.Repository('/home/jdavid/sandboxes/pygit2/')
>>> bid = r.create_blob('')
>>> b = r[bid] # Empty blob
>>> print(b.diff_to_buffer('hello').patch)
diff --git a/file b/file
index e69de29..b6fc4c6 100644
--- a/file
+++ b/file
@@ -0,0 +1 @@
+hello
\ No newline at end of file

That said, solution 2 looks good to me, then you can support the optional arguments, old and new filenames. In that case you would wrap git_patch_from_blob_and_buffer no? Then the name could be Patch.from_blob_and_buffer so it matches libgit2's name (wonder why one is called _to_ and the other is called _and_)

[jdavid]

Developing solution 2 a bit further, it could type check the arguments and wrap:

• git_patch_from_blob_and_buffer
• git_patch_from_blobs
• git_patch_from_buffers

Then it could be called Patch.create_from, maybe.

[brandonio21]

Thanks for the reply, @jdavid.

Unfortunately, the solution you highlighted with the empty blob does not work. It creates a patch that is an addition to an empty file, not the creation of a new file (patch should have new file and be --- /dev/null

In either case, glad that there is approval of the second "proper" solution. I'll work on it