RFR: 8354469: Keytool exposes the password in plain text when command is piped using | grep

[Weijun Wang]

Add more description on password handling into the keytool man page. A link to the man page is now added to the keytool help screen.

When keytool output is redirected into a file or file, a warning is shown:

$ keytool -genkeypair | type

Warning: password will be echoed because output is redirected.
Enter keystore password:  password
Warning: password will be echoed because output is redirected.
Re-enter new password:


A new manual test is added.

Sorry we cannot suppress password echoing in this case at the moment because `System.console()` is not available.

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Commit messages:
 - tests
 - show warning when echo is on
 - link and man page changes

Changes: https://git.openjdk.org/jdk/pull/24805/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24805&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8354469
  Stats: 219 lines in 11 files changed: 166 ins; 18 del; 35 mod
  Patch: https://git.openjdk.org/jdk/pull/24805.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24805/head:pull/24805

PR: https://git.openjdk.org/jdk/pull/24805