b2sum, md5sum, sha*sum: add --ignore-missing example (#7929)

pages/common/b2sum.md

@@ -11,10 +11,18 @@
 
 `b2sum {{path/to/file1}} {{path/to/file2}}`
 
-- Read a file of BLAKE2 sums and filenames and verify all files have matching checksums:
-
-`b2sum -c {{path/to/file.b2}}`
-
 - Calculate the BLAKE2 checksum from stdin:
 
 `{{some_command}} | b2sum`
+
+- Read a file of BLAKE2 sums and filenames and verify all files have matching checksums:
+
+`b2sum --check {{path/to/file.b2}}`
+
+- Only show a message for missing files or when verification fails:
+
+`b2sum --check --quiet {{path/to/file.b2}}`
+
+- Only show a message for files for which verification fails, ignoring missing files:
+
+`b2sum --ignore-missing --check --quiet {{path/to/file.b2}}`