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 129' HUP
 108         trap 'exit 130' INT
 109         trap 'exit 131' QUIT
 110         trap 'exit 134' ABRT
 111         trap 'exit 141' PIPE
 112         trap 'exit 143' TERM
 113         git cat-file blob "$1" >"$basef" 2>/dev/null || exit 1
 114         git cat-file blob "$2" >"$oursf" 2>/dev/null || exit 1
 115         git cat-file blob "$3" >"$thrsf" 2>/dev/null || exit 1
 116         git merge-file --quiet "$oursf" "$basef" "$thrsf" >/dev/null 2>&1 || exit 1
 117         printf '%s\n' "Auto-merging $4"
 118         newhash="$(git hash-object -w --stdin <"$oursf" 2>/dev/null)" || exit 1
 119 fi
 120
 121 [ -n "$newhash" ] && [ -n "$newmode" ] || exit 1
 122 [ "$newhash" != "$nullsha" ] || newmode="0"
 123 git update-index --index-info >/dev/null 2>&1 <<EOT
 124 0 $nullsha$tab$4
 125 $newmode $newhash$tab$4
 126 EOT