doc/bugs/git_annex_forget_--drop-dead_can_lose_group_information.mdwn

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+### Please describe the problem.
+
+If multiple remotes edit group information and one of them does `git annex forget --force --drop-dead` some of those edits can be lost on sync.
+
+### What steps will reproduce the problem?
+
+Make a temporary directory and `cd` into it. Then run this script:
+
+[[!format sh """
+#!/bin/bash
+
+git annex version
+
+git init a
+cd a
+git annex init
+touch test
+git annex add test
+git annex sync
+cd ..
+git clone a b
+cd b
+git annex sync
+
+cd ../a
+git annex group here ga
+git annex sync
+cd ../b
+git annex group here gb
+git annex forget --force --drop-dead
+git annex sync
+
+cd ../a
+git annex sync
+cd ../b
+git annex sync
+
+cd ../a
+echo "A IS IN GROUP:"
+git annex group .
+cd ../b
+echo "B IS IN GROUP:"
+git annex group .
+
+"""]]
+
+
+### What version of git-annex are you using? On what operating system?
+
+6.20170101-1+deb9u2 on Debian Stretch but I also tested this occurs in version 6.20180719
+
+### Please provide any additional information below.
+
+Here's the output of the above script. The interesting part is the last two lines which show that remote 'b' is not in any group despite being added to group 'gb'.
+
+[[!format sh """
+git-annex version: 6.20170101.1
+build flags: Assistant Webapp Pairing Testsuite S3(multipartupload)(storageclasses) WebDAV Inotify DBus DesktopNotify ConcurrentOutput TorrentParser MagicMime Feeds Quvi
+key/value backends: SHA256E SHA256 SHA512E SHA512 SHA224E SHA224 SHA384E SHA384 SHA3_256E SHA3_256 SHA3_512E SHA3_512 SHA3_224E SHA3_224 SHA3_384E SHA3_384 SKEIN256E SKEIN256 SKEIN512E SKEIN512 SHA1E SHA1 MD5E MD5 WORM URL
+remote types: git gcrypt p2p S3 bup directory rsync web bittorrent webdav tahoe glacier ddar hook external
+Initialized empty Git repository in /home/matthew/test-git-annex/a/.git/
+init  ok
+(recording state in git...)
+add test ok
+(recording state in git...)
+commit  
+[master (root-commit) ffcf48d] git-annex in matthew@thorium:~/test-git-annex/a
+ 1 file changed, 1 insertion(+)
+ create mode 120000 test
+ok
+Cloning into 'b'...
+done.
+(merging origin/git-annex into git-annex...)
+commit  (recording state in git...)
+
+On branch master
+Your branch is up-to-date with 'origin/master'.
+nothing to commit, working tree clean
+ok
+pull origin 
+ok
+push origin 
+Counting objects: 3, done.
+Delta compression using up to 4 threads.
+Compressing objects: 100% (3/3), done.
+Writing objects: 100% (3/3), 409 bytes | 0 bytes/s, done.
+Total 3 (delta 0), reused 0 (delta 0)
+To /home/matthew/test-git-annex/a
+ * [new branch]      git-annex -> synced/git-annex
+ok
+group here ok
+(recording state in git...)
+commit  
+On branch master
+nothing to commit, working tree clean
+ok
+group here ok
+(recording state in git...)
+forget git-annex (recording state in git...)
+ok
+(recording state in git...)
+commit  
+On branch master
+Your branch is up-to-date with 'origin/master'.
+nothing to commit, working tree clean
+ok
+pull origin 
+remote: Counting objects: 3, done.
+remote: Compressing objects: 100% (3/3), done.
+remote: Total 3 (delta 0), reused 0 (delta 0)
+Unpacking objects: 100% (3/3), done.
+From /home/matthew/test-git-annex/a
+   e9a879d..000eb8e  git-annex  -> origin/git-annex
+ok
+(merging origin/git-annex into git-annex...)
+(recording state in git...)
+(recording state in git...)
+push origin 
+Counting objects: 11, done.
+Delta compression using up to 4 threads.
+Compressing objects: 100% (10/10), done.
+Writing objects: 100% (11/11), 1.03 KiB | 0 bytes/s, done.
+Total 11 (delta 3), reused 0 (delta 0)
+To /home/matthew/test-git-annex/a
+ + e9a879d...00986fa git-annex -> synced/git-annex (forced update)
+ok
+(merging synced/git-annex into git-annex...)
+(recording state in git...)
+commit  
+On branch master
+nothing to commit, working tree clean
+ok
+commit  
+On branch master
+Your branch is up-to-date with 'origin/master'.
+nothing to commit, working tree clean
+ok
+pull origin 
+remote: Counting objects: 3, done.
+remote: Compressing objects: 100% (3/3), done.
+remote: Total 3 (delta 0), reused 0 (delta 0)
+Unpacking objects: 100% (3/3), done.
+From /home/matthew/test-git-annex/a
+ + 000eb8e...965b6af git-annex  -> origin/git-annex  (forced update)
+ok
+(merging origin/git-annex into git-annex...)
+A IS IN GROUP:
+ga
+B IS IN GROUP:
+"""]]
+
+### Have you had any luck using git-annex before? (Sometimes we get tired of reading bug reports all day and a lil' positive end note does wonders)
+
+Yes, git-annex is slowly replacing all of my other sync and backup systems I've cobbled together over the years.