commit 7927e442f3b7c154bcd0b7e836dc2e4a800c9e1b
author Ke Wu <mikewu@google.com> Thu Aug 20 14:43:30 2020 -0700
committer Ke Wu <mikewu@google.com> Thu Aug 20 15:13:57 2020 -0700
tree 85c47f79db6dd172554fa170a81dda289ddbeafb
parent 202dbcf322561cd3f6b04b4faecb9c62ba97fe42

cos_image_analyzer: Add some details in user guide.

This CL has the following changes:
1) polish the user guide:
 - Stress that The -local input expects disk.raw file. So users need to
 unzip tarball if needed.
 - Explain the service account credentials that required by -gcs input
 and add link to the instruction.
 - Correct the default list of -compressRootfs flag.
 - Explain why root is needed for the program.
 - Delete words about commits and release notes from the usage because
 they are not implemented yet.

 2) Change the default value of -package flag from true to false.
 Because the feature is not ready yet.

 3) Allow to choose whether to authenticate when downloading from GCS.
 This is useful to download public data from GCS.

Change-Id: Id602b4e27abeb2ea0a7238fb62ab6b6164cdc8e4