Currently rclone check supports matching two file trees by sizes and hashes.
This change adds support for SUM files produced by GNU utilities like sha1sum.
Fixes#1005
Note: checksum by default checks, hashsum by default prints sums.
New flag is named "--checkfile" but carries hash name.
Summary of introduced command forms:
```
rclone check sums.sha1 remote:path --checkfile sha1
rclone checksum sha1 sums.sha1 remote:path
rclone hashsum sha1 remote:path --checkfile sums.sha1
rclone sha1sum remote:path --checkfile sums.sha1
rclone md5sum remote:path --checkfile sums.md5
```
This commit modifies the operations.hashSum function by adding an alternate code path. This code path is triggered by passing downloadFlag = True. When activated, rclone will download files from the remote and hash them locally. downloadFlag = False preserves the existing behavior of using the remote to retrieve the hash.
This commit modifies HashLister to support the new hashSum method as well as consolidating the roles of HashLister, HashListerBase64, Md5sum, and Sha1sum. The printing of hashes from the function defined in HashLister has been revised to work with --progress. There are light changes to operations.syncFprintf and cmd.startProgress for this.
The unit test operations_test.TestHashSums is modified to support this change and test the download functionality.
The command functions hashsum, md5sum, sha1sum, and dbhashsum are modified to support this change. A download flag has been added and an output-file flag has been added. The output-file flag writes hashes to a file instead of stdout to avoid the need to redirect stdout.
In f544234 we removed the global flags from each command as it was
making each page very big and causing 1000s of lines of duplication in
the man page.
This change adds a new flags page with all the global flags on and
links each command page to it.
Fixes#3273
* put the most up to date docs into the code
* generate command docs using rclone gendocs
* put command docs into own directory
* remake them into MANUAL.md
