Repository: borgbackup/borg

Issue:
can't use --chunker-params to achieve bigger chunks
I would like to use bigger chunks up to 32Mb (and maybe bigger), but it does not work, what I'm doing wrong?

```shell
willy@browar: ~/borg # borg create -s --chunker-params 19,25,21,4095 /tmp/borgtest::test1 /root/borg/                                                                                                 
usage: borg create [-h] [--critical] [--error] [--warning] [--info] [--debug]                      
                   [--debug-topic TOPIC] [-p] [--log-json]                                         
                   [--lock-wait SECONDS] [--show-version] [--show-rc]                              
                   [--no-files-cache] [--umask M] [--remote-path PATH]                             
                   [--remote-ratelimit RATE] [--consider-part-files]                               
                   [--debug-profile FILE] [-n] [-s] [--list]                                       
                   [--filter STATUSCHARS] [--json] [--no-cache-sync]                               
                   [-e PATTERN] [--exclude-from EXCLUDEFILE]                                       
                   [--pattern PATTERN] [--patterns-from PATTERNFILE]                               
                   [--exclude-caches] [--exclude-if-present NAME]                                  
                   [--keep-exclude-tags] [-x] [--numeric-owner] [--noatime]                        
                   [--noctime] [--ignore-inode] [--files-cache MODE]                               
                   [--read-special] [--comment COMMENT]                                            
                   [--timestamp TIMESTAMP] [-c SECONDS]                                            
                   [--chunker-params PARAMS] [-C COMPRESSION]                                      
                   ARCHIVE [PATH [PATH ...]]     
borg create: error: argument --chunker-params: invalid ChunkerParams value: '19,25,21,4095'        
willy@browar: ~/borg # borg create -s --chunker-params 19,23,21,4095 /tmp/borgtest::test1 /root/borg/                                                                                                 
------------------------------------------------------------------------------
Archive name: test1
Archive fingerprint: 8e660562d23f25035b2e309301f02b74810968f82d51d56a79b1125aafeac331
Time (start): Mon, 2017-10-09 19:14:47
Time (end):   Mon, 2017-10-09 19:14:48
Duration: 0.35 seconds
Number of files: 370
Utilization of max. archive size: 0%
------------------------------------------------------------------------------
                       Original size      Compressed size    Deduplicated size
This archive:               24.99 MB             19.06 MB             19.06 MB
All archives:               24.99 MB             19.06 MB             19.06 MB

                       Unique chunks         Total chunks
Chunk index:                     374                  375
------------------------------------------------------------------------------
```


Discussion:
IIRC, 8MB is the maximum as that is our buffer size.

Why do you want more than that?
IT is related to this: https://github.com/borgbackup/borg/pull/3116
But in this case it does'nt make any sense.
Maybe it should be mentioned in the docs?
Thanks 

Resolving patch:
diff --git a/src/borg/archiver.py b/src/borg/archiver.py
--- a/src/borg/archiver.py
+++ b/src/borg/archiver.py
@@ -2686,9 +2686,6 @@ def define_archive_filters_group(subparser, *, sort_by=True, first_last=True):
         and not include any other contents of the containing folder, this can be enabled
         through using the ``--keep-exclude-tags`` option.
 
-        Borg respects the nodump flag. Files flagged nodump will be marked as excluded (x)
-        in ``--list`` output.
-
         Item flags
         ++++++++++
 
@@ -3292,13 +3289,13 @@ def define_archive_filters_group(subparser, *, sort_by=True, first_last=True):
 
             borg delete borg
 
-        Unless ``--inplace`` is specified, the upgrade process first
-        creates a backup copy of the repository, in
-        REPOSITORY.before-upgrade-DATETIME, using hardlinks. This takes
-        longer than in place upgrades, but is much safer and gives
-        progress information (as opposed to ``cp -al``). Once you are
-        satisfied with the conversion, you can safely destroy the
-        backup copy.
+        Unless ``--inplace`` is specified, the upgrade process first creates a backup
+        copy of the repository, in REPOSITORY.before-upgrade-DATETIME, using hardlinks.
+        This requires that the repository and its parent directory reside on same
+        filesystem so the hardlink copy can work.
+        This takes longer than in place upgrades, but is much safer and gives
+        progress information (as opposed to ``cp -al``). Once you are satisfied
+        with the conversion, you can safely destroy the backup copy.
 
         WARNING: Running the upgrade in place will make the current
         copy unusable with older version, with no way of going back


Test patch: