Document PAT creation and hint in alr publish help

doc/publishing.md

@@ -22,6 +22,30 @@ index on GitHub on your behalf.
 Read on for the details underlying these automated steps, or in case you need
 to perform further tweaking.
 
+## Creating a Github Personal Access Token
+
+A Personal Access Token (PAT) allows Alire to act on your behalf to fork the
+community index, push the new release manifest to a new branch in your own fork,
+and finally open a pull-request against the community repository.
+
+The PAT, once created, is a plain string. You can either export the environment
+variable `GH_TOKEN` set to this string, or provide it when Alire asks for it.
+
+There are two kinds of PATs on Github: classic and fine-grained. The latter are
+in beta and not documented here yet. Follow these steps to create a classic PAT:
+
+1. On the main https://github.com page, after having logged in, click on your
+   profile photo on the top-right corner.
+1. Click on "Settings" in the list of options in the profile menu.
+1. Click on "Developer settings" entry at the bottom in your Settings page.
+1. Click on "Personal access tokens" and then "Tokens (classic)".
+1. Click on "Generate new token" and the select the classic variant.
+1. In the "Select scopes" section, under "repo", check "public_repo". This is
+   the only permission needed for this PAT.
+1. Click on "Generate token" at the bottom.
+
+You will get the PAT string after completing the generation.
+
 ## General concepts
 
 The community index is a collection of

src/alr/alr-commands-publish.ads

@@ -20,7 +20,7 @@ package Alr.Commands.Publish is
    function Long_Description (Cmd : Command)
                               return AAA.Strings.Vector
    is (AAA.Strings.Empty_Vector
-       .Append ("Checks a release and generates an index manifest")
+       .Append ("Checks a release and generates an index manifest.")
        .New_Line
        .Append ("See full details at")
        .New_Line
@@ -34,6 +34,10 @@ package Alr.Commands.Publish is
                 & " issue `alr publish` after committing and pushing"
                 & " the new release version.")
        .New_Line
+       .Append ("See the above link for instructions on how to create a "
+         & "Github Personal Access Token (PAT), needed to allow `alr` to "
+         & "interact with Github (forking, PR creation) on your behalf.")
+       .New_Line
        .Append ("Use --tar to create a source archive ready to be uploaded.")
        .New_Line
        .Append ("Use --manifest to use metadata in a non-default file.")