Handle indentation when parsing sandbox_image

[cartermckinnon]

Issue #, if available:

Resolves #767

Description of changes:

Handles indentation on the sandbox_image key of the containerd config file. Works by just converting this line to valid bash and source-ing it. TOML comments are ignored because they're valid bash comments.

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Testing Done

Executed:

#!/usr/bin/env bash

INDENTED=$(mktemp)

echo '[plugins]
  [plugins."io.containerd.grpc.v1.cri"]
    # sandbox_image comment about the sandbox_image
    sandbox_image = "one"' >> $INDENTED

FLAT=$(mktemp)

echo '[plugins]
[plugins."io.containerd.grpc.v1.cri"]
# sandbox_image comment about the sandbox_image
sandbox_image = "two"' >> $FLAT

source <(grep "sandbox_image" $INDENTED | tr -d ' ')
echo "$sandbox_image"

source <(grep "sandbox_image" $FLAT | tr -d ' ')
echo "$sandbox_image"

Output:

one
two

[guessi]

I though it's a danger more to use "grep" here.

Imagine there's a comment line with "sandbox_image" but it just a comment?

[cartermckinnon]

TOML comments use a hash symbol (#) like bash, so it "just works". There's an example of this to my testing section in the description.

https://github.com/toml-lang/toml/blob/main/toml.md#user-content-comment

[bwagner5]

very clever! LGTM