Automatically fix Syncthing conflicts via 3-way merges (requires trashbin versioning or stronger, as well as fd, ripgrep, and git)

readme.md

Replace shebang with following if Nix is installed to automatically pull in dependencies.

#!/usr/bin/env nix-shell
#! nix-shell -i bash -p git fd ripgrep

fix-conflicts.bash

#!/usr/bin/env bash

# syncthing share. some parent directory
targetShare="$PWD"
while true; do
        if [ -d "$targetShare/.stfolder" ]; then break; fi
        if [ "$targetShare" == "/" ]; then
                echo "Could not find parent Syncthing share"
                exit 1;
        fi
        targetShare=$(realpath "$targetShare/..")
done 

# search scope
fdArgs="--no-ignore"
# regex to detect sync conflicts
conflictRegex='\.sync-conflict-[0-9]+-[0-9]{6}-[A-Z0-9]{7}(\..+)?$'
# regex to detect if file is in progress of being merged
mergeRegex='^<<<<<<< .+$\n(.*\n)*^=======$\n(.*\n)*^>>>>>>> .+$\n'

sharePath="${PWD#"$targetShare/"}"
conflicts="$(fd "$conflictRegex" . --type file $fdArgs)"

if [ "$conflicts" == "" ]; then echo "No conflicts, exiting."; exit 0; fi

count=$(echo "%s" "$conflicts" | wc -l)
countLen=$(printf "%d" "$count" | wc -c)

echo "Fixing $count conflict(s) via 3-way merge:"; 

echo "$conflicts" | while read -r path; do
        i=$((${i:-0} + 1))

        dir=$(dirname "$path")
        name=$(basename "$path")
        sanitizedName="$(echo "$name" | sed -r "s/$conflictRegex//")"
        extension="$(echo "$name" | rev | cut -d. -f1 | rev)" # might be empty

        # find paths for 3-way merge
        base="$dir/$sanitizedName"
        ancestors="$(fd \
                "$(echo "$sanitizedName" | sed -r "s/\.$extension\$//")" \
                "$targetShare/.stversions/$sharePath/$dir" \
                --type file $fdArgs 2>/dev/null)"
        other="$path"

        printf "[$(printf "%0${countLen}d" "$i")/$count] Merging '%s': " "$(echo "$base" | sed -r 's/^\.\///')"
        # pick "latest" ancestor
        ancestor="$(echo "$ancestors" | sort -hr | head -1)"

        # if no common ancestor, try empty file
        ancestor="${ancestor:-/dev/null}"

        # check if base even exists
        if [ ! -f "$base" ]; then echo "conflict file references non-existant base, skipping."; continue; fi
        if rg --quiet --multiline "$mergeRegex" "$base"; then echo "file has pending manual merge, skipping."; continue; fi

        # perform actual merge
        git merge-file "$base" "$ancestor" "$other" 2>/dev/null

        # for documentation on exit codes, see: `man git-merge-file`
        mergeStatus="$?"
        if [ "$mergeStatus" -eq 255 ]; then echo "can't merge binary files, skipping."; continue; fi
        if [ "$mergeStatus" -gt 127 ]; then echo "could not perform merge due to unknown error ($mergeStatus)."; continue; fi
        if [ "$mergeStatus" -eq 0 ]; then echo "merged cleanly."; rm "$other"; continue; fi
        if [ "$mergeStatus" -lt 0 ]; then echo "could not perform merge due to error ($mergeStatus)."; continue; fi
        if [ "$mergeStatus" -gt 0 ]; then echo "needs manual intervention for $mergeStatus merge(s)."; rm "$other"; continue; fi
done