### Bug description

👋 thanks again for quarto. the more i use it, the more i am appreciating it. 

I am reporting this here with quarto rather than knitr because it changes for me from `1.1.251` -> `1.2.148`.

I also tested on the dev version with this HEAD (https://github.com/quarto-dev/quarto-cli/commit/5da03618fedf82742fac3635364a8074f11d3d3e) and the issue was this present. As of `1.2.148` I can't knit child qmds that are in a separate folder. I can reproduce with these two files:

````md
---
title: "Untitled"
execute: 
  eval: true
  echo: false
  warning: false
format: html
---

```{r r-pkgs}
library(dplyr)
library(gt)
library(purrr)
```
# Tables

::: {.panel-tabset}

```{r}
#| output: asis
res <- purrr::map_chr(unique(starwars$homeworld), \(hw) {
    knitr::knit_child(
      input = "child-dir/_child.qmd", 
      envir = environment(), 
      quiet = TRUE
      )
  })

cat(res, sep = '\n')
```
:::
````

### child-dir/_child.qmd
 
````md
## `r hw`

```{r}
#| echo: false
starwars %>%
  filter(homeworld == hw) %>%
  count(sex) %>%
  head() %>%
  gt()
```
````

Here is the error I am getting: 
> Error in readLines(con, warn = FALSE) : cannot open the connection
Calls: .main ... <Anonymous> -> enumerate_output_formats -> read_utf8 -> readLines
In addition: Warning message:
In readLines(con, warn = FALSE) :
  cannot open file '_child.qmd': No such file or directory
>
> Execution halted

This works if the child qmds are in the same directory as the main qmd. 

### Checklist

- [X] Please include a minimal, fully reproducible example in a single .qmd file? Please provide the whole file rather than the snippet you believe is causing the issue.
- [X] Please [format your issue](https://quarto.org/bug-reports.html#formatting-make-githubs-markdown-work-for-us) so it is easier for us to read the bug report.
- [X] Please document the RStudio IDE version you're running (if applicable), by providing the value displayed in the "About RStudio" main menu dialog?
- [X] Please document the operating system you're running. If on Linux, please provide the specific distribution.
cderv
2022-09-22T21:17:14Z
boshek
bug needs-repro
v1.3
closed
Can't knit child qmds in a sub-directory
https://github.com/quarto-dev/quarto-cli/issues/2566