Clean up Earthfile a little and add comments

Author: Jaykul

Earthfile

@@ -23,34 +23,34 @@ bootstrap:
         && git config --global user.name "Earthly Build"
     # I'm using Invoke-Build tasks from this other repo which rarely changes
     COPY tasks+tasks/* /Tasks
-    # Dealing with dependencies first allows docker to cache packages for us
-    # So the dependency cach only re-builds when you add a new dependency
+    # Dealing with dependencies first allows earthly (docker) to cache layers for us
+    # So the dependency cache only re-builds when you change the list in these files
     COPY build.requires.psd1 .
     # COPY *.csproj .
     RUN ["pwsh", "-File", "/Tasks/_Bootstrap.ps1", "-RequiresPath", "build.requires.psd1"]
 
 build:
     FROM +bootstrap
     RUN mkdir $OUTPUT_ROOT $TEST_ROOT $TEMP_ROOT
+    # make sure you have output folders (like bin, obj, Modules) in .earthlyignore
+    # NOTE: we copy .git because we use GitVersion in the build to calculate the version
+    #       To avoid that, we could pass the version as an ARG
     COPY . .
-    # make sure you have bin and obj in .earthlyignore, as their content from context might cause problems
     RUN ["pwsh", "-Command", "Invoke-Build", "-Task", "Build", "-File", "Build.build.ps1"]
 
     # SAVE ARTIFACT [--keep-ts] [--keep-own] [--if-exists] [--force] <src> [<artifact-dest-path>] [AS LOCAL <local-path>]
     SAVE ARTIFACT $OUTPUT_ROOT/$MODULE_NAME AS LOCAL ./Modules/$MODULE_NAME
 
 test:
-    # If we run a target as a reference in FROM or COPY, it's outputs will not be produced
     FROM +build
-    # make sure you have bin and obj in .earthlyignore, as their content from context might cause problems
     RUN ["pwsh", "-Command", "Invoke-Build", "-Task", "Test", "-File", "Build.build.ps1"]
 
     # re-output the build output so we can rely on running just +test locally
     SAVE ARTIFACT $OUTPUT_ROOT/$MODULE_NAME AS LOCAL ./Modules/$MODULE_NAME
     SAVE ARTIFACT $TEST_ROOT AS LOCAL ./Modules/$MODULE_NAME-TestResults
 
 all:
-    BUILD +build
+    # If we only reference with FROM (or COPY) the outputs will not be produced
     BUILD +test
     FROM +build
     RUN --push --secret NUGET_API_KEY --secret PSGALLERY_API_KEY -- \