tg--index-merge-one-file.sh

   1 #!/bin/sh
   2
   3 # tg--index-merge-one-file -- auto merge a file without touching working tree
   4 # Copyright (C) 2017 Kyle J. McKay
   5 # All rights reserved.
   6 # License GPLv2+
   7
   8 # $TG_TMP_DIR => location to store temporary files
   9 # $tg_index_mergetop_behavior => "" (ours), "theirs", "merge", "remove"
  10 # $1          => stage 1 hash or empty
  11 # $2          => stage 2 hash or empty
  12 # $3          => stage 3 hash or empty
  13 # $4          => full pathname in index
  14 # $5          => stage 1 mode (6 octal digits) or empty
  15 # $6          => stage 2 mode
  16 # $7          => stage 3 mode
  17
  18 nullsha="0000000000000000000000000000000000000000"
  19 tab='   '
  20
  21 if [ "$1" = "-h" ] && [ $# -eq 1 ]; then
  22         echo "\
  23 usage: ${tgname:-tg} index-merge-one-file [--<mergetop>] <s1_hash> <s2_hash> <s3_hash> <path> <s1_mode> <s2_mode> <s3_mode>"
  24         exit 0
  25 fi
  26 if [ -z "$tg_index_mergetop_behavior" ]; then case "$1" in
  27         --merge|--theirs|--remove|--ours)
  28                 tg_index_mergetop_behavior="${1#--}"
  29                 shift
  30 esac; fi
  31
  32 [ $# -eq 7 ] || exit 1
  33
  34 # The read-tree --aggressive option handles three cases that may end up in
  35 # here:
  36 #
  37 #  1. One side removes a file but the other leaves it unchanged (remove)
  38 #  2. Both sides remove a file (remove)
  39 #  3. Both sides add a path identically (use it)
  40 #
  41 # The problem is (1).  When resolving .topdeps and .topmsg files using either
  42 # --ours or --theirs the normal resolution of (1) to remove may be incorrect.
  43 #
  44 # But that means in order to get that case to come to us all three cases must
  45 # be handled properly for non-topfile files since they will therefore end up
  46 # in here as well.
  47
  48 newhash=
  49 newmode="${6:-0}"
  50
  51 if [ "$tg_index_mergetop_behavior" != "merge" ] &&
  52    { [ "$4" = ".topdeps" ] || [ "$4" = ".topmsg" ]; }
  53 then
  54         # Handle --ours, --theirs and --remove for .topdeps and .topmsg
  55
  56         if [ "$tg_index_mergetop_behavior" = "remove" ]; then
  57                 newhash="$nullsha"
  58         elif [ "$tg_index_mergetop_behavior" = "theirs" ]; then
  59                 newhash="${3:-$nullsha}"
  60                 newmode="${7:-0}"
  61         else
  62                 # --ours is the default mode
  63                 newhash="${2:-$nullsha}"
  64         fi
  65
  66         # .topmsg and .topdeps are never executable
  67         [ "$newmode" != "100755" ] || newmode="100644"
  68
  69         if [ "$newmode" != "100644" ] && [ "$newhash" != "$nullsha" ]; then
  70                 # .topmsg and .topdeps are only allowed to be blobs
  71                 newhash="$nullsha"
  72                 newmode="0"
  73         fi
  74 fi
  75
  76 if [ -z "$newhash" ]; then
  77         # Check for the "--aggressive" and "--trivial" things:
  78         #
  79         # a) all three hashes are the same (handled same as next case)
  80         # b) $2 and $3 are the same (and their modes)
  81         # c) $1 and $2 are the same (and their modes)
  82         # d) $1 and $3 are the same (and their modes)
  83
  84         if [ "$2" = "$3" ] && [ "$6" = "$7" ] ; then
  85                 newhash="${2:-$nullsha}"
  86         elif [ "$1" = "$2" ] && [ "$5" = "$6" ]; then
  87                 newhash="${3:-$nullsha}" newmode="${7:-0}"
  88         elif [ "$1" = "$3" ] && [ "$5" = "$7" ]; then
  89                 newhash="${2:-$nullsha}"
  90         fi
  91 fi
  92
  93 if [ -z "$newhash" ]; then
  94         # We only handle auto merging existing files with the same mode
  95         case "${1:-:}${2:-:}${3:-:}${4:-:}${5:-:}${6:-:}${7:-:}" in *":"*) exit 1; esac
  96         [ "$5" = "$6" ] && [ "$6" = "$7" ] || exit 1
  97
  98         # mode must match 100\o\o\o
  99         case "$6" in 100[0-7][0-7][0-7]);;*) exit 1; esac
 100
 101         # perform a "simple" 3-way merge
 102         tg_tmp_dir="${TG_TMP_DIR:-/tmp}"
 103         basef="$tg_tmp_dir/tgmerge_$$_base"
 104         oursf="$tg_tmp_dir/tgmerge_$$_ours"
 105         thrsf="$tg_tmp_dir/tgmerge_$$_thrs"
 106         trap 'rm -f "$basef" "$oursf" "$thrsf"' EXIT
 107         trap 'exit' HUP INT QUIT ABRT PIPE TERM
 108         git cat-file blob "$1" >"$basef" 2>/dev/null || exit 1
 109         git cat-file blob "$2" >"$oursf" 2>/dev/null || exit 1
 110         git cat-file blob "$3" >"$thrsf" 2>/dev/null || exit 1
 111         git merge-file --quiet "$oursf" "$basef" "$thrsf" >/dev/null 2>&1 || exit 1
 112         printf '%s\n' "Auto-merging $4"
 113         newhash="$(git hash-object -w --stdin <"$oursf" 2>/dev/null)" || exit 1
 114 fi
 115
 116 [ -n "$newhash" ] && [ -n "$newmode" ] || exit 1
 117 [ "$newhash" != "$nullsha" ] || newmode="0"
 118 git update-index --index-info >/dev/null 2>&1 <<EOT
 119 0 $nullsha$tab$4
 120 $newmode $newhash$tab$4
 121 EOT