tutorial/getting-started: better explain object identifiers

When the tutorial references blob identifiers in the output,
also immediately explain the syntax. Also emphasize the possible
abbreviations made possible by b9880e8ecdce02f047dfb1d19de5f1ed07a82ac6
given that they are typically used in practise.

Co-authored-by: Klaus Aehlig <aehlig@linta.de>

1 files changed, 19 insertions, 2 deletions

diff --git a/doc/tutorial/getting-started.org b/doc/tutorial/getting-started.org
index c77d261b..033309fb 100644
--- a/doc/tutorial/getting-started.org
+++ b/doc/tutorial/getting-started.org
@@ -63,8 +63,10 @@ INFO: Artifacts built, logical paths are:
 $
 #+END_SRC
 
-The subcommand ~build~ just builds the binary but does not stage it to any
-user-defined location on the file system. To also stage the produced artifact to
+The subcommand ~build~ just builds the artifact but does not stage it to any
+user-defined location on the file system. Instead it reports a description
+of the artifact consisting of ~git~ blob identifier, size, and type (in
+this case ~f~ for non-executable file). To also stage the produced artifact to
 the working directory, use the ~install~ subcommand and specify the output
 directory:
 
@@ -96,3 +98,18 @@ $ just install-cas [557db03de997c86a4a028e1ebd3a1ceb225be238:12:f]
 Hello World
 $
 #+END_SRC
+
+The canonical way of requesting an object from the CAS is, as just shown, to
+specify the full triple of hash, size, and type, separated by colons and
+enclosed in square brackets. To simplify usage, the brackets can be omitted
+and the size and type fields have the default values ~0~ and ~f~, respectively.
+While the default value for the size is wrong for all but one string, the hash
+still determines the content of the file and hence the local CAS is still
+able to retrieve the file. So the typical invocation would simply specify the
+hash.
+
+#+BEGIN_SRC sh
+$ just install-cas 557db03de997c86a4a028e1ebd3a1ceb225be238
+Hello World
+$
+#+END_SRC