Added a comment

doc/bugs/data_loss_from_dedup_when_v7_unlocked_file_is_duplicated__47__truncated/comment_2_6ed0b157c18487b3bda365efa92b3c0e._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="2019-02-24T06:41:01Z"
+ 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-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\"
+		
+		PTRFILES=()
+		HAVETRUNCS=
+		
+		while IFS= read -r -d '' line; do
+			IFS=\" \" f=( $line )
+			if [ \"${f[0]}\" != \"D\" ]; then #skip non-deletes
+				continue
+			fi
+			
+			$GIT checkout -- \"${f[1]}\" #restore
+			if [ -n \"$(grep -F --text '/annex/objects' ${f[1]})\" ]; then #is broken annex pointer file
+				echo \"${f[1]} is a pointer file\"
+				HAVETRUNCS=1
+				truncate -s 0 \"${f[1]}\" #truncate
+				PTRFILES+=(\"${f[1]}\") #track
+				$GIT add \"${f[1]}\" #stage content change
+			else
+				echo \"${f[1]} is not a pointer file\"
+				rm \"${f[1]}\"
+			fi
+		done < <($GIT status --porcelain=1 -z) #status in null-delimited machine readable format
+		
+		if [ -n \"$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)\"
+    }
+"""]]