Oh-my-fish: Omf error when installing multiple themes

[pydo]

fish info:
```» omf doctor
Oh My Fish version: 6
OS type: Linux
Fish version: fish, version 2.7.1
Git version: git version 2.17.1
Git core.autocrlf: no

**Description**
`omf` outputs an error when installing the following themes:
- `cbjohnson`
- `chain`
- `lambda`

**Repro**
1. `omf install cbjohnson`
2. `omf install chain`
3. `omf install lambda`

**Expected behavior**
3. The lambda package should install without returning any errors and should be set
as my current theme. I'm assuming this is an issue with `omf` not properly swapping prompts after I installed a new theme

**Actual behavior**

 ```
» omf install lambda
Updating https://github.com/oh-my-fish/packages-main master... Done!
Installing package lambda
✔ lambda successfully installed.
Conflicting prompt setting.
Run omf doctor and fix issues before continuing.
user at user-desktop in ~

doctor output:

user at user-desktop in ~
» omf doctor
Oh My Fish version:   6
OS type:              Linux
Fish version:         fish, version 2.7.1
Git version:          git version 2.17.1
Git core.autocrlf:    no
Warning: fish_prompt.fish is overridden.
  fish_config command persists the prompt to ~/.config/fish/functions/fish_prompt.fish
  That file takes precedence over Oh My Fish's themes. Remove the file to fix it:
  rm ~/.config/fish/functions/fish_prompt.fish

If everything you use Oh My Fish for is working fine, please don't worry and just ignore the warnings. Thanks!

Why doesn't omf have a command for setting/enabling themes? The only available theme commands seem to be install and list. But what if I want to enable a theme that I already installed?

I resolved the issue by deleting my old ~/.config/fish/functions/fish_prompt.fish, so I'm actually opening this issue as a bug report.
I'd appreciate any input, thanks!

[oranja]

The command for switching themes (from installed ones) is omf theme <theme_name>.
e.g. omf theme chain.

That being said, I suspect that there's still a bug with this, where the previous theme sticks even after selecting a different theme, and you have to run omf reload.

[pydo]

@oranja Were you able to repro this issue following the steps I listed? If not, I can try to make a docker image that will consistently reproduce this bug.

[oranja]

Yes @pydo I can reproduce this with the steps you listed. Thank you for the detailed report.
I will investigate further as soon as I get a chance.

[nerosnm]

I have this problem every time I try to switch themes using omf theme <theme_name>, and am forced to delete my fish_prompt.fish file every time.

In addition, when I run omf theme toaster, for example, I receive the following message:

Conflicting prompt setting.
Run omf doctor and fix issues before continuing.
Theme not installed!
Install it using omf install toaster

But when I run omf install toaster as instructed, I receive the following, inconsistent, message:

Updating https://github.com/oh-my-fish/packages-main master... Done!
Error: toaster already installed.
Conflicting prompt setting.
Run omf doctor and fix issues before continuing.

[jhimon]

Maybe there is problem with lambda theme. Remove it by omf remove lambda.
Worked for me

[ColtonIdle]

You might be running into https://github.com/oh-my-fish/oh-my-fish/issues/671