git-subtree.sh

   1 #!/bin/bash
   2 #
   3 # git-subtree.sh: split/join git repositories in subdirectories of this one
   4 #
   5 # Copyright (C) 2009 Avery Pennarun <apenwarr@gmail.com>
   6 #
   7 if [ $# -eq 0 ]; then
   8     set -- -h
   9 fi
  10 OPTS_SPEC="\
  11 git subtree add --prefix=<prefix> <commit>
  12 git subtree split [options...] --prefix=<prefix> <commit...>
  13 git subtree merge --prefix=<prefix> <commit>
  14 git subtree pull  --prefix=<prefix> <repository> <refspec...>
  15 --
  16 h,help        show the help
  17 q             quiet
  18 prefix=       the name of the subdir to split out
  19  options for 'split'
  20 onto=         try connecting new tree to an existing one
  21 rejoin        merge the new branch back into HEAD
  22 ignore-joins  ignore prior --rejoin commits
  23 "
  24 eval $(echo "$OPTS_SPEC" | git rev-parse --parseopt -- "$@" || echo exit $?)
  25 . git-sh-setup
  26 require_work_tree
  27
  28 quiet=
  29 command=
  30 onto=
  31 rejoin=
  32 ignore_joins=
  33
  34 debug()
  35 {
  36         if [ -z "$quiet" ]; then
  37                 echo "$@" >&2
  38         fi
  39 }
  40
  41 assert()
  42 {
  43         if "$@"; then
  44                 :
  45         else
  46                 die "assertion failed: " "$@"
  47         fi
  48 }
  49
  50
  51 #echo "Options: $*"
  52
  53 while [ $# -gt 0 ]; do
  54         opt="$1"
  55         shift
  56         case "$opt" in
  57                 -q) quiet=1 ;;
  58                 --prefix) prefix="$1"; shift ;;
  59                 --no-prefix) prefix= ;;
  60                 --onto) onto="$1"; shift ;;
  61                 --no-onto) onto= ;;
  62                 --rejoin) rejoin=1 ;;
  63                 --no-rejoin) rejoin= ;;
  64                 --ignore-joins) ignore_joins=1 ;;
  65                 --no-ignore-joins) ignore_joins= ;;
  66                 --) break ;;
  67         esac
  68 done
  69
  70 command="$1"
  71 shift
  72 case "$command" in
  73         add|merge|pull) default= ;;
  74         split) default="--default HEAD" ;;
  75         *) die "Unknown command '$command'" ;;
  76 esac
  77
  78 if [ -z "$prefix" ]; then
  79         die "You must provide the --prefix option."
  80 fi
  81 dir="$prefix"
  82
  83 if [ "$command" != "pull" ]; then
  84         revs=$(git rev-parse $default --revs-only "$@") || exit $?
  85         dirs="$(git rev-parse --no-revs --no-flags "$@")" || exit $?
  86         if [ -n "$dirs" ]; then
  87                 die "Error: Use --prefix instead of bare filenames."
  88         fi
  89 fi
  90
  91 debug "command: {$command}"
  92 debug "quiet: {$quiet}"
  93 debug "revs: {$revs}"
  94 debug "dir: {$dir}"
  95 debug "opts: {$*}"
  96 debug
  97
  98 cache_setup()
  99 {
 100         cachedir="$GIT_DIR/subtree-cache/$$"
 101         rm -rf "$cachedir" || die "Can't delete old cachedir: $cachedir"
 102         mkdir -p "$cachedir" || die "Can't create new cachedir: $cachedir"
 103         debug "Using cachedir: $cachedir" >&2
 104 }
 105
 106 cache_get()
 107 {
 108         for oldrev in $*; do
 109                 if [ -r "$cachedir/$oldrev" ]; then
 110                         read newrev <"$cachedir/$oldrev"
 111                         echo $newrev
 112                 fi
 113         done
 114 }
 115
 116 cache_set()
 117 {
 118         oldrev="$1"
 119         newrev="$2"
 120         if [ "$oldrev" != "latest_old" \
 121              -a "$oldrev" != "latest_new" \
 122              -a -e "$cachedir/$oldrev" ]; then
 123                 die "cache for $oldrev already exists!"
 124         fi
 125         echo "$newrev" >"$cachedir/$oldrev"
 126 }
 127
 128 find_existing_splits()
 129 {
 130         debug "Looking for prior splits..."
 131         dir="$1"
 132         revs="$2"
 133         git log --grep="^git-subtree-dir: $dir\$" \
 134                 --pretty=format:'%s%n%n%b%nEND' "$revs" |
 135         while read a b junk; do
 136                 case "$a" in
 137                         git-subtree-mainline:) main="$b" ;;
 138                         git-subtree-split:) sub="$b" ;;
 139                         *)
 140                                 if [ -n "$main" -a -n "$sub" ]; then
 141                                         debug "  Prior: $main -> $sub"
 142                                         cache_set $main $sub
 143                                         echo "^$main^ ^$sub^"
 144                                         main=
 145                                         sub=
 146                                 fi
 147                                 ;;
 148                 esac
 149         done
 150 }
 151
 152 copy_commit()
 153 {
 154         # We're doing to set some environment vars here, so
 155         # do it in a subshell to get rid of them safely later
 156         git log -1 --pretty=format:'%an%n%ae%n%ad%n%cn%n%ce%n%cd%n%s%n%n%b' "$1" |
 157         (
 158                 read GIT_AUTHOR_NAME
 159                 read GIT_AUTHOR_EMAIL
 160                 read GIT_AUTHOR_DATE
 161                 read GIT_COMMITTER_NAME
 162                 read GIT_COMMITTER_EMAIL
 163                 read GIT_COMMITTER_DATE
 164                 export  GIT_AUTHOR_NAME \
 165                         GIT_AUTHOR_EMAIL \
 166                         GIT_AUTHOR_DATE \
 167                         GIT_COMMITTER_NAME \
 168                         GIT_COMMITTER_EMAIL \
 169                         GIT_COMMITTER_DATE
 170                 (echo -n '*'; cat ) |  # FIXME
 171                 git commit-tree "$2" $3  # reads the rest of stdin
 172         ) || die "Can't copy commit $1"
 173 }
 174
 175 add_msg()
 176 {
 177         dir="$1"
 178         latest_old="$2"
 179         latest_new="$3"
 180         cat <<-EOF
 181                 Add '$dir/' from commit '$latest_new'
 182
 183                 git-subtree-dir: $dir
 184                 git-subtree-mainline: $latest_old
 185                 git-subtree-split: $latest_new
 186         EOF
 187 }
 188
 189 merge_msg()
 190 {
 191         dir="$1"
 192         latest_old="$2"
 193         latest_new="$3"
 194         cat <<-EOF
 195                 Split '$dir/' into commit '$latest_new'
 196
 197                 git-subtree-dir: $dir
 198                 git-subtree-mainline: $latest_old
 199                 git-subtree-split: $latest_new
 200         EOF
 201 }
 202
 203 toptree_for_commit()
 204 {
 205         commit="$1"
 206         git log -1 --pretty=format:'%T' "$commit" -- || exit $?
 207 }
 208
 209 subtree_for_commit()
 210 {
 211         commit="$1"
 212         dir="$2"
 213         git ls-tree "$commit" -- "$dir" |
 214         while read mode type tree name; do
 215                 assert [ "$name" = "$dir" ]
 216                 echo $tree
 217                 break
 218         done
 219 }
 220
 221 tree_changed()
 222 {
 223         tree=$1
 224         shift
 225         if [ $# -ne 1 ]; then
 226                 return 0   # weird parents, consider it changed
 227         else
 228                 ptree=$(toptree_for_commit $1)
 229                 if [ "$ptree" != "$tree" ]; then
 230                         return 0   # changed
 231                 else
 232                         return 1   # not changed
 233                 fi
 234         fi
 235 }
 236
 237 copy_or_skip()
 238 {
 239         rev="$1"
 240         tree="$2"
 241         newparents="$3"
 242         assert [ -n "$tree" ]
 243
 244         identical=
 245         p=
 246         for parent in $newparents; do
 247                 ptree=$(toptree_for_commit $parent) || exit $?
 248                 if [ "$ptree" = "$tree" ]; then
 249                         # an identical parent could be used in place of this rev.
 250                         identical="$parent"
 251                 fi
 252                 if [ -n "$ptree" ]; then
 253                         parentmatch="$parentmatch$parent"
 254                         p="$p -p $parent"
 255                 fi
 256         done
 257
 258         if [ -n "$identical" -a "$parentmatch" = "$identical" ]; then
 259                 echo $identical
 260         else
 261                 copy_commit $rev $tree "$p" || exit $?
 262         fi
 263 }
 264
 265 ensure_clean()
 266 {
 267         if ! git diff-index HEAD --exit-code --quiet; then
 268                 die "Working tree has modifications.  Cannot add."
 269         fi
 270         if ! git diff-index --cached HEAD --exit-code --quiet; then
 271                 die "Index has modifications.  Cannot add."
 272         fi
 273 }
 274
 275 cmd_add()
 276 {
 277         if [ -e "$dir" ]; then
 278                 die "'$dir' already exists.  Cannot add."
 279         fi
 280         ensure_clean
 281
 282         set -- $revs
 283         if [ $# -ne 1 ]; then
 284                 die "You must provide exactly one revision.  Got: '$revs'"
 285         fi
 286         rev="$1"
 287
 288         debug "Adding $dir as '$rev'..."
 289         git read-tree --prefix="$dir" $rev || exit $?
 290         git checkout "$dir" || exit $?
 291         tree=$(git write-tree) || exit $?
 292
 293         headrev=$(git rev-parse HEAD) || exit $?
 294         if [ -n "$headrev" -a "$headrev" != "$rev" ]; then
 295                 headp="-p $headrev"
 296         else
 297                 headp=
 298         fi
 299         commit=$(add_msg "$dir" "$headrev" "$rev" |
 300                  git commit-tree $tree $headp -p "$rev") || exit $?
 301         git reset "$commit" || exit $?
 302 }
 303
 304 cmd_split()
 305 {
 306         debug "Splitting $dir..."
 307         cache_setup || exit $?
 308
 309         if [ -n "$onto" ]; then
 310                 debug "Reading history for --onto=$onto..."
 311                 git rev-list $onto |
 312                 while read rev; do
 313                         # the 'onto' history is already just the subdir, so
 314                         # any parent we find there can be used verbatim
 315                         debug "  cache: $rev"
 316                         cache_set $rev $rev
 317                 done
 318         fi
 319
 320         if [ -n "$ignore_joins" ]; then
 321                 unrevs=
 322         else
 323                 unrevs="$(find_existing_splits "$dir" "$revs")"
 324         fi
 325
 326         # We can't restrict rev-list to only "$dir" here, because that leaves out
 327         # critical information about commit parents.
 328         debug "git rev-list --reverse --parents $revs $unrevs"
 329         git rev-list --reverse --parents $revs $unrevs |
 330         while read rev parents; do
 331                 debug
 332                 debug "Processing commit: $rev"
 333                 exists=$(cache_get $rev)
 334                 if [ -n "$exists" ]; then
 335                         debug "  prior: $exists"
 336                         continue
 337                 fi
 338                 debug "  parents: $parents"
 339                 newparents=$(cache_get $parents)
 340                 debug "  newparents: $newparents"
 341
 342                 tree=$(subtree_for_commit $rev "$dir")
 343                 debug "  tree is: $tree"
 344                 [ -z $tree ] && continue
 345
 346                 newrev=$(copy_or_skip "$rev" "$tree" "$newparents") || exit $?
 347                 debug "  newrev is: $newrev"
 348                 cache_set $rev $newrev
 349                 cache_set latest_new $newrev
 350                 cache_set latest_old $rev
 351         done || exit $?
 352         latest_new=$(cache_get latest_new)
 353         if [ -z "$latest_new" ]; then
 354                 die "No new revisions were found"
 355         fi
 356
 357         if [ -n "$rejoin" ]; then
 358                 debug "Merging split branch into HEAD..."
 359                 latest_old=$(cache_get latest_old)
 360                 git merge -s ours \
 361                         -m "$(merge_msg $dir $latest_old $latest_new)" \
 362                         $latest_new >&2
 363         fi
 364         echo $latest_new
 365         exit 0
 366 }
 367
 368 cmd_merge()
 369 {
 370         ensure_clean
 371
 372         set -- $revs
 373         if [ $# -ne 1 ]; then
 374                 die "You must provide exactly one revision.  Got: '$revs'"
 375         fi
 376         rev="$1"
 377
 378         git merge -s subtree $rev
 379 }
 380
 381 cmd_pull()
 382 {
 383         ensure_clean
 384         set -x
 385         git pull -s subtree "$@"
 386 }
 387
 388 "cmd_$command" "$@"