Support Image History

[baronfel]

The history field of the Image Manifest is used as a log of what commands/who made modifications to the image. It's generally added to on a layer-by-layer basis, and if it is maintained correctly, you get nice displays in outputs like docker image history:

➜ docker history container-app-tres:0.0.6
IMAGE          CREATED         CREATED BY                                      SIZE      COMMENT
229b57e74fb4   7 seconds ago   dotnet publish -p:PublishProfile=DefaultCont…   8.38MB    A dynamically-generated image layer from the .NET SDK
<missing>      10 days ago     /bin/sh -c #(nop) COPY dir:b0ac707752044c30c…   21.3MB
<missing>      10 days ago     /bin/sh -c #(nop)  ENV ASPNET_VERSION=7.0.0-…   0B
<missing>      10 days ago     /bin/sh -c ln -s /usr/share/dotnet/dotnet /u…   24B
<missing>      10 days ago     /bin/sh -c #(nop) COPY dir:99ddbc873c8fc6285…   72.9MB
<missing>      10 days ago     /bin/sh -c #(nop)  ENV DOTNET_VERSION=7.0.0-…   0B
<missing>      10 days ago     /bin/sh -c #(nop)  ENV ASPNETCORE_URLS=http:…   0B
<missing>      10 days ago     /bin/sh -c apt-get update     && apt-get ins…   37MB
<missing>      2 weeks ago     /bin/sh -c #(nop)  CMD ["bash"]                 0B
<missing>      2 weeks ago     /bin/sh -c #(nop) ADD file:0eae0dca665c7044b…   80.4MB

and the Docker Desktop image history view:

A simple addition to the AddLayer function makes this possible:

var history = new JsonObject();
history["created"] = DateTime.UtcNow;
history["author"] = ".NET SDK";
history["created_by"] = "dotnet publish -p:PublishProfile=DefaultContainer";
history["comment"] = "A dynamically-generated image layer from the .NET SDK";
config["history"]!.AsArray().Add(history);

But I wanted to slow down and think about what data we would want to embed in this structure. The spec has the following to say about it:

Should we put package/SDK versions in this? Should the created date be the actual now? I know we've been thinking about determinism in this project, but the history property isn't part of digest calculation.