Re: [PATCH v2 2/2] [GSOC] ref-filter: introduce enum atom_type

"ZheNing Hu via GitGitGadget" [off-list ref] writes:

the enum value of `ATOM_UNKNOWN` is equals to zero, which

s/the/The/;

could ensure that we can easily distinguish such a struct
where the atom_type is known from such a struct where it
is unknown yet.

the enum value of `ATOM_INVALID` is equals to the size of

Ditto.

+/*
+ * The enum atom_type is used as the coordinates of valid_atom entry.
+ * In the atom parsing stage, it will be passed to used_atom.atom_type
+ * as the identifier of the atom type. We can judge the type of used_atom
+ * entry by `if (used_atom[i].atom_type == ATOM_*)`.
+ *
+ * ATOM_UNKNOWN equals to 0, used as an enumeration value of uninitialized
+ * atom_type.

Shouldn't it be (-1)?

And I'd assume I am right in the following.

+ * ATOM_INVALID equals to the size of valid_atom array, which could help us
+ * iterate over valid_atom array like this:
+ *
+ * 	for (i = ATOM_UNKNOWN + 1; i < ATOM_INVALID; i++) {

I find it far more intuitive to say

	for (i = 0; i < ATOM_INVALID; i++)

than having to say UNKNOWN+1.

In any case, the values should be indented, and a comment should
ensure that the final one stays at the end, perhaps like this.

	enum atom_type {
		ATOM_INVALID = -2,
		ATOM_UNKNOWN = -1,
		ATOM_REFNAME,
		...
		ATOM_ELSE,
		ATOM_MAX /* MUST BE AT THE END */
	}

(note that the trailing comma is deliberately omitted).

It would allow people to say

	for (i = 0; i < ATOM_MAX; i++)

instead, which would be even nicer.