During the variable substitution, if a missing variable was followed
by an existing one, the empty "outerErr" variable overwrote the previous
non-empty variable.

Unlike with Docker Compose v1, the first found error did not guarantee
that an actual error would be thrown.

Example which would have run before the fix even though var1 is not defined:

```yaml
services:
  bash:
    image: bash:5.0.18-alpine3.15
    environment:
      var12: "_ ${var1:?Error1} _ ${var2:?Error2} _ "
    command:
      - env
```

```bash
```

This change also means that, if multiple variables are missing in one string, the first one will be reported by Docker Compose

Signed-off-by: Ákos Takács <takacs.akos@it-sziget.hu>

Some Windows editors tend to add UTF-8 BOM markers to files,
which breaks parsing of `.env` files.

Now, when the file is read, if it starts with a UTF-8 BOM,
we'll skip it. (`.env` files are always processed as UTF-8.)

See docker/compose#9799.

Signed-off-by: Milas Bowman <milas.bowman@docker.com>

Bumps [github.com/docker/go-units](https://github.com/docker/go-units) from 0.4.0 to 0.5.0.
- [Release notes](https://github.com/docker/go-units/releases)
- [Commits](docker/go-units@v0.4.0...v0.5.0)

---
updated-dependencies:
- dependency-name: github.com/docker/go-units
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

…b.com/docker/go-units-0.5.0

Bump github.com/docker/go-units from 0.4.0 to 0.5.0

dotenv: fix parse error on files with UTF-8 BOM

…ept-last

Fix required env vars ignored except the last one

The parser was too strict here and would reject valid constructs
that used an unescaped `$` that was not part of a variable
expression (and not ambiguous).

Now, only errors for unmatched braced expressions (e.g. `${FOO`)
are returned, but other valid cases are ignored and the `$` will
be treated literally, e.g. `a $ string` -> `a $ string`, which is
the same as in POSIX.

Signed-off-by: Milas Bowman <milas.bowman@docker.com>

Signed-off-by: Guillaume Lours <705411+glours@users.noreply.github.com>

* Handle standard escape sequences based on XSI/XBD
  https://pubs.opengroup.org/onlinepubs/9699919799/utilities/echo.html
* Fix parsing with escaped quotes at end of quoted
  value
* Handle key whose name starts with `export` (require
  whitespace between `export` keyword when stripping)
* Fix parsing of unquoted values with embedded `#`
  (require a space before starting an inline comment)
* Use correct parser methods throughout all test cases
* Eliminate a lot of unused code that was not working
  right

Signed-off-by: Milas Bowman <milas.bowman@docker.com>