feat: add data uri scheme encoding as valid source

[MatthewDolan]

Proposed Solution (2.b.) from #310.

Example Usage

Without additional sources:

example_config=$(cat <<EOF
description = "Description for example"
binaries = ["example"]
channel "unstable" {
 update = "5m"
 source = "git@github.com:cashapp/example.git#$EXAMPLE_VERSION"
}
EOF
)

override_sources=$(cat <<EOF
{"example": $(echo "$example_config" | jq -R -s '.')}
EOF
)

override_uri="data:application/json;base64,$(echo "$override_sources" | base64)"

HERMIT_ADDITIONAL_SOURCES="$override_uri" hermit ...

Example URI

> echo "$override_uri"
data:application/json;base64,eyJleGFtcGxlIjogImRlc2NyaXB0aW9uID0gXCJEZXNjcmlwdGlvbiBmb3IgZXhhbXBsZVwiCmJpbmFyaWVzID0gW1wiZXhhbXBsZVwiXQpjaGFubmVsIFwidW5zdGFibGVcIiB7CiB1cGRhdGUgPSBcIjVtXCIKIHNvdXJjZSA9IFwiZ2l0QGdpdGh1Yi5jb206Y2FzaGFwcC9leGFtcGxlLmdpdCNtYWluXCIKfQoifQo

[alecthomas]

Hi sorry I took so long to respond!

I don't like the ergonomics of this 😢 - it is objectively not an improvement over creating a temporary directory, which is a similar amount of shell, more straightforward, and already works:

tmpsource="$(mktemp -d)"
trap 'rm -rf "${tmpsource}"' EXIT INT ERR
cat  > "$tmpsource/example.hcl" <<EOF
description = "Description for example"
binaries = ["example"]
channel "unstable" {
 update = "5m"
 source = "git@github.com:cashapp/example.git#$EXAMPLE_VERSION"
}
EOF
export HERMIT_ADDITIONAL_SOURCES="file://${tmpsource}"

I wonder though, if the most common case isn't overriding a single package? If that is true, we could have a dedicated envar for a single package. Something like:

export HERMIT_PACKAGE_OVERRIDE='
name = "example"
description = "Description for example"
binaries = ["example"]
channel "unstable" {
 update = "5m"
 source = "git@github.com:cashapp/example.git#$EXAMPLE_VERSION"
}
'

We could add an extra, optional, name attribute to a package to simplify how this is represented.

[alecthomas]

Another idea; introduce an additional higher-level HCL block specifically for this mechanism eg.

export HERMIT_PACKAGE_OVERRIDES='
package example {
  description = "Description for example"
  binaries = ["example"]
  channel "unstable" {
    update = "5m"
    source = "git@github.com:cashapp/example.git#$EXAMPLE_VERSION"
  }
}
'

[MatthewDolan]

Another idea; introduce an additional higher-level HCL block specifically for this mechanism eg.

I like this idea the best! It's concise, readable, and doesn't require editing disk.

If I find a free moment, I will prototype something up. It's a little more than trivial because some of the code separation expects map[string]string so either I need to parse and then un-parse the hcl or I need to move some interfaces around.

[MatthewDolan]

After further thought, I agree that this is the right path forward.

#313 (comment)

Closing the PR for now.