chezmoi add mishandles cases where entry or parent is external

[twpayne]

Describe the bug

As reported by @dhruvinsh in #1205, chezmoi add fails if the path is in a directory implicitly created by an external.

To reproduce

similar to this another issue found, file: .chezmoiexternal.toml

[".oh-my-zsh"]
    type = "archive"
    url = "https://github.com/ohmyzsh/ohmyzsh/archive/master.tar.gz"
    exact = true
    stripComponents = 1
[".oh-my-zsh/custom/plugins/zsh-syntax-highlighting"]
    type = "archive"
    url = "https://github.com/zsh-users/zsh-syntax-highlighting/archive/master.tar.gz"
    exact = true
    stripComponents = 1

Everything is working as expect with chezmoi apply. But now while my config is managed by chezmoi I decided to add aliases in .oh-my-zsh/custom/aliases.zsh. and I wanted to track it by chezmoi but when i try to add it by chezmoi I receive below error

> ~ chezmoi add .oh-my-zsh/custom/aliases.zsh
chezmoi: stat /home/ds/.local/share/chezmoi/https:/github.com/ohmyzsh/ohmyzsh/archive/master.tar.gz: no such file or directory

Expected behavior

chezmoi add adds the file.

[dhruvinsh]

@twpayne I would like to point out something here:
Issue #2006 and issue #1574 (this issue) have somewhat similarity but still I believe they are different.

In issue #2006 I had .config/nvim being managed by .chezmoiexternal and I was trying to add .config/direnv (a separate) directory. Thus I was getting error:

chezmoi: mkdir /home/ds/.local/share/chezmoi/dot_config/direnv: no such file or directory

But here in this case, .chezmoiexternal is managing .oh-my-zsh and .oh-my-zsh/custom/plugins/zsh-syntax-highlighting. And when trying to add .oh-my-zsh/custom/aliases.zsh (same root as one of the .chezmoiexternal) chezmoi give below erro:

chezmoi: stat /home/ds/.local/share/chezmoi/https:/github.com/ohmyzsh/ohmyzsh/archive/master.tar.gz: no such file or directory

I tried few test and it seems that workaround only works if mkdir error persists. But in case of state error then workaround does not work and which made me believe that #2006 and this issue are different.

[twpayne]

When this issue is fixed, we should also update the docs to include Felipe's neat trick in this comment.

[twpayne]

This also applies to files. See #3559 (comment).

[koiralakiran1]

Adding the workaround reference here, as this issue seems more prominent. Mentioned in #2006 (comment)

Temporary work around applied:

Manually create a dot_config directory and within that directory touch .keep to force chezmoi to track it.

now using chezmoi add ~/.config/direnv/direnvrc works as expected.

In addition to this you'll need to make your externals exact = false in the externals toml that conflict. Eg: .chezmoiexternal.toml

[".oh-my-zsh"]
    type = "archive"
    url = "https://github.com/ohmyzsh/ohmyzsh/archive/master.tar.gz"
    exact = false
    stripComponents = 1