Added a comment

doc/bugs/data_loss_from_dedup_when_v7_unlocked_file_is_duplicated__47__truncated/comment_2_5395837d61947644930285e65a4a8529._comment

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+[[!comment format=mdwn
+ username="david.j.buckmaster@984ff2704feacab53415ac5647206517d18f88f8"
+ nickname="david.j.buckmaster"
+ avatar="http://cdn.libravatar.org/avatar/1650cdf23a0999fd0e03650e20c90ee7"
+ subject="comment 2"
+ date="2019-02-24T07:01:35Z"
+ content="""
+In case this is NOT a bug but rather an incompatibility between borg/git-annex, the bash snippet below seems to sidestep the issue if run AFTER a borg operation but BEFORE any other annex commit/sync. Unsure if I'm the only person in the world that wants a not-permanently-append-only borg repository in an unlocked+thin git-annex...but...after a borg operation that truncates+deletes files, the function uses the status printout to identify all missing, borg-controlled files, and for each
+
+1. Reverts the deletion (git checkout -- ..)
+2. Checks if the restored file is a (dead) file pointer (file contents start with /annex/objects). If no, redo the delete and continue loop; if yes, truncate (but do not delete) the file and stage a commit.
+
+Truncations are then committed to force annex to see that contents have changed, and all deletions are repeated. After that, git annex add-ing a new file with old content restores the annex content that borg truncated, rather than ending up with a pointer file and missing contents.
+
+Test case:
+
+	set -x && \
+		mkdir tmp && cd tmp && \
+		git init && \
+		git-annex init  --version 7 base && \
+		git-annex config --set annex.thin true && \
+		\
+		echo \"bar\">foo && cat foo && git-annex add foo && ls -l && git-annex sync && git-annex unlock foo && git-annex sync && \
+		echo \"barbar\">foo && cat foo && rm foo && \
+		\
+		git checkout -- foo && truncate -s 0 foo && git add foo && git-annex sync && \
+		rm foo && git-annex sync && \
+		\
+		echo \"bar\">ffoo && cat ffoo && git-annex add ffoo && git-annex sync && cat ffoo
+
+Bash function:
+
+	handleborgdeletes() {
+		echo \"(handleborgdeletes\"
+		
+		local PTRFILES=()
+		local HAVETRUNCS=
+		local f
+		
+		for f in $(IFS=$'\n' $GITANNEX status | grep ^D | grep -E '(index|hints|integrity|data/)'); do
+			f=${f:2}
+			
+			$GIT checkout -- \"$f\" #restore
+			if [ -n \"$(grep -F --text '/annex/objects' $f)\" ]; then #is broken annex pointer file
+				echo \"$f is a pointer file\"
+				HAVETRUNCS=1
+				truncate -s 0 \"$f\" #truncate
+				PTRFILES+=(\"$f\") #track
+				$GIT add \"$f\" #stage content change
+			else
+				echo \"$f is not a pointer file\"
+				rm \"$f\"
+			fi
+		done
+		
+		if [ -n \"$HAVETRUNCS\" ]; then
+			$GIT commit -m \"truncating borg deletions\" #commit content changes
+			
+			for f in ${PTRFILES[@]}; do
+				rm \"$f\" #repeat delete to be committed later
+			done
+		fi
+		echo \"handleborgdeletes)\"
+	}
+"""]]