Update what-is-git.asc

[aziz58]

• [x] I provide my work under the project license.
• [x] I grant such license of my work as is required for the purposes of future print editions to Ben Straub and Scott Chacon.

Changes

Context

[solt87]

I assume the intent of this change is to harmonize the text with the diagram and its caption, which to me seems self-evident. But I think there's a bigger issue here: the portion on the screenshot seems to assume that "working tree" is the same as "working directory", and this change would use "working directory" consistently (at least taking into account @ben's suggestion). However, according to the Git glossary, "tree", "tree object" and "working tree" mean different things, with "tree" being _"[...] equivalent to a directory". Whereas the "working tree" "[...] normally contains the contents of the HEAD commit’s tree, plus any local changes that you have made but not yet committed."_ (My emphasis.)

I think the two decent options would be to either explain both "working tree" and "working directory", and use the terms consistently and correctly, or (and maybe this is preferable in an introductory textbook) use the two terms interchangeably, but mention in parentheses that they aren't exactly the same, with a reference to the glossary.

(I won't even bring up the fact that there is another related term, "worktree", which seems to be different from "working tree", as this complicates an already convoluted matter further. :) )