cg-merge

   1 #!/usr/bin/env bash
   2 #
   3 # Merge a branch to the current branch
   4 # Copyright (c) Petr Baudis, 2005
   5 #
   6 # Takes a parameter identifying the branch to be merged, defaulting
   7 # to 'origin' or the current branch's default remote branch, see `cg-fetch`
   8 # for details).
   9 #
  10 # This command merges all changes currently in the given branch to your
  11 # current branch. This can produce a merging commit on your branch sticking
  12 # the two branch together (so-called 'tree merge'). However in case there
  13 # are no changes in your branch that wouldn't be in the remote branch, no
  14 # merge commit is done and commit pointer of your branch is just updated
  15 # to the last commit on the remote branch (so-called 'fast-forward merge').
  16 #
  17 # In case of conflicts being generated by the merge, you have to examine
  18 # the tree (cg-merge will tell you which files contain commits; the commits
  19 # are denoted by rcsmerge-like markers <<<<, ====, and >>>>) and then do
  20 # `cg-commit` yourself. `cg-commit` will know that you are committing a merge
  21 # and will record it properly.
  22 #
  23 # Note that when you are merging remote branches, `cg-merge` will use them
  24 # in the state they are currently at in your repository. If you want to
  25 # fetch the latest changes from the remote repository, use `cg-fetch`. If you
  26 # want to fetch the changes and then merge them to your branch, use the command
  27 # `cg-update`.
  28 #
  29 # Also note that if you have local changes in your tree that you did not
  30 # commit, cg-merge will always preserve them when fast-forwarding. When doing
  31 # a tree merge, it will preserve them if they don't conflict with the merged
  32 # changes, and report an error otherwise. In short, it should do the Right
  33 # Thing (tm), never lose your local changes and never let them mix up with
  34 # the merge.
  35 #
  36 # OPTIONS
  37 # -------
  38 # -b BASE_COMMIT:: Specify the base commit for the merge
  39 #       Parameter specifies the base commit for the merge. Otherwise, the
  40 #       least common ancestor is automatically selected.
  41 #
  42 # -j:: Join current branch with BRANCH_NAME
  43 #       Join the current branch and BRANCH_NAME together. This makes sense
  44 #       when the branches have no common history, meaning they are actually
  45 #       not branches related at all as far as GIT is concerned. Merging such
  46 #       branches might be a user error and you well may be doing something
  47 #       you do not want; but equally likely, you may actually WANT to join
  48 #       the projects together, which is what this option does.
  49 #
  50 # -n:: Disable autocommitting
  51 #       Parameter specifies that you want to have tree merge never
  52 #       autocommitted, but want to review and commit it manually. This will
  53 #       basically make cg-merge always behave like there were conflicts
  54 #       during the merge.
  55 #
  56 # --squash:: Use "squash" merge to record pending commits as a single merge commit
  57 #       "Squash" merge - condense all the to-be-merged commits to a single
  58 #       merge commit. This means "throw away history of the branch I'm
  59 #       merging", essentially like in CVS or SVN, with the same problem -
  60 #       re-merging with that branch later will cause trouble. This is not
  61 #       recommended unless you actually really want to flatten the history
  62 #       of the merged branch, e.g. when merging topical branches to your
  63 #       mainline (you want to have the logical change you developed in
  64 #       a branch as a single "do it" commit instead of a sequence of
  65 #       "do it I", "fix it", "do it II", "fix it II", "fix it III" commits
  66 #       like you would get with a regular merge).
  67 #
  68 # -v:: Enable verbosity
  69 #       Display more verbose output - most notably list all the files
  70 #       touched by the merged changes.
  71 #
  72 # HOOKS
  73 # -----
  74 # '.git/hooks/merge-pre' BRANCH BASE CURHEAD MERGEDHEAD MERGETYPE::
  75 #       If the file exists and is executable it will be executed right
  76 #       before the merge itself happens. The merge is cancelled if the script
  77 #       returns non-zero exit code.
  78 #        - MERGETYPE is either "forward", "squash", or "tree".
  79 #
  80 # '.git/hooks/merge-post' BRANCH BASE CURHEAD MERGEDHEAD MERGETYPE STATUS::
  81 #       If the file exists and is executable it will be executed after
  82 #       the merge is done.
  83 #        - MERGETYPE is either "forward", "squash", or "tree".
  84 #        - For 'forward', the STATUS is "ok" or "localchanges", while for
  85 #         "squash" and "tree" the STATUS can be "localchanges", "conflicts",
  86 #          "nocommit", or "ok".
  87
  88 # Developer's documentation:
  89 #
  90 # ENVIRONMENT
  91 # -----------
  92 # _cg_orig_head::
  93 #       The original commit ID of the to-be-merged branch, if cg-merge
  94 #       is called right after fetch. This is used to do better decision
  95 #       about whether to fast-forward or tree-merge.
  96
  97 # Testsuite: Largely covered (t92xx testsuite family, incomplete coverage;
  98 # missing: hooks, -n, -b, --squash)
  99
 100 USAGE="cg-merge [-n] [-b BASE_COMMIT] [-j] [--squash] [-v] [BRANCH_NAME]"
 101 _git_requires_root=1
 102
 103 . "${COGITO_LIB}"cg-Xlib || exit 1
 104
 105
 106 prehook()
 107 {
 108         if [ -x "$_git/hooks/merge-pre" ]; then
 109                 "$_git/hooks/merge-pre" "$branchname" "$base" "$head" "$branch" "$@" || die "merge cancelled by hook"
 110         fi
 111 }
 112
 113 posthook()
 114 {
 115         if [ -x "$_git/hooks/merge-post" ]; then
 116                 "$_git/hooks/merge-post" "$branchname" "$base" "$head" "$branch" "$@"
 117         fi
 118 }
 119
 120
 121 head="$(cg-object-id -c)" || exit 1
 122
 123
 124 careful=
 125 base=
 126 join=
 127 squash=
 128 verbose=
 129 while optparse; do
 130         if optparse -n; then
 131                 careful=1
 132         elif optparse -c; then
 133                 warn "cg-merge -c is deprecated, cg-merge -n is the new flag name"
 134                 careful=1
 135         elif optparse -b=; then
 136                 base="$(cg-object-id -c "$OPTARG")" || exit 1
 137         elif optparse -j; then
 138                 join=1
 139         # -s reserved to strategy
 140         elif optparse --squash; then
 141                 squash=1
 142         elif optparse -v; then
 143                 verbose=1
 144         else
 145                 optfail
 146         fi
 147 done
 148
 149 branchname="${ARGS[0]}"
 150 [ "$branchname" ] || branchname="$(choose_origin branches "what to merge?")" || exit 1
 151 branch=$(cg-object-id -c "$branchname") || exit 1
 152
 153 [ "$base" ] || base="$(git-merge-base --all "$head" "$branch")"
 154 if [ ! "$join" ]; then
 155         [ "$base" ] || die "unable to automatically determine merge base (consider cg-merge -j)"
 156         baselist=($base)
 157         if [ "${#baselist[@]}" -gt "1" ]; then
 158                 echo "Multiple merge base candidates, please select one manually (by running cg-merge -b BASE [BRANCH]):"
 159                 echo "${baselist[*]}" | tr ' ' '\n'
 160                 echo
 161                 conservative_merge_base "${baselist[@]}" # -> _cg_baselist
 162                 echo -n "The most conservative base (but likely a lot of conflicts): "
 163                 echo "${_cg_baselist[*]}"
 164                 exit 3
 165         fi >&2
 166
 167 else
 168         [ "$base" ] && die "joining branches with common history is something I refuse to do"
 169         index="$(mktemp -t gitmerge.XXXXXX)" || exit $?
 170         GIT_INDEX_FILE="$index" git-read-tree
 171         base="$(GIT_INDEX_FILE="$index" git-write-tree)"
 172         rm "$index"
 173 fi
 174
 175
 176 [ -s "$_git/blocked" ] && die "merge blocked: $(cat "$_git/blocked")"
 177 # Deprecated as of 2006-11-17
 178 [ -s "$_git/merging" ] && die "old-style merge state detected, panicking; you upgraded cogito in the middle of a merge! redo the merge, cg-reset will bring you back to the starting line"
 179
 180 statedir="$_git/cg-merge-state"
 181
 182 if [ -s "$statedir/merging" ] && grep -q "$branch" "$statedir/merging"; then
 183         echo "Branch already merged in the working tree." >&2
 184         exit 0
 185 fi
 186
 187 if [ "$base" = "$branch" ]; then
 188         echo "Branch already fully merged." >&2
 189         exit 0
 190 fi
 191
 192 if { [ "$head" = "$base" ] || [ "$head" = "$_cg_orig_head" ]; } && [ ! "$squash" ] && [ ! -s "$statedir/merging" ]; then
 193         # No need to do explicit merge with a merge commit; just bring
 194         # the HEAD forward.
 195
 196         echo "Fast-forwarding $base -> $branch" >&2
 197         echo -e "\ton top of $head ..." >&2
 198
 199         [ "$verbose" ] && git-diff-tree --abbrev -r "$(cg-object-id -t "$head")" "$(cg-object-id -t "$branch")"
 200
 201         prehook forward
 202         if ! tree_timewarp "forward" "yes, rollback (or rather rollforth) the tree!" "$head" "$branch"; then
 203                 posthook forward localchanges
 204                 exit 1
 205         fi
 206         posthook forward ok
 207
 208         exit 0
 209 fi
 210
 211
 212 git-update-index --refresh >/dev/null
 213
 214 if [ ! "$squash" ]; then
 215         [ -s "$statedir/squashing" ] && die "cannot combine squashing and non-squashing merges"
 216
 217         echo "Merging $base -> $branch" >&2
 218         echo -e "\tto $head ..." >&2
 219
 220         mergetype="tree"
 221 else
 222         echo "Squashing $base -> $branch" >&2
 223         echo -e "\ton top of $head ..." >&2
 224
 225         mergetype="squash"
 226 fi
 227
 228 [ "$verbose" ] && git-diff-tree --abbrev -r "$(cg-object-id -t "$base")" "$(cg-object-id -t "$branch")"
 229
 230 prehook "$mergetype"
 231
 232 mkdir -p "$statedir"
 233
 234 git-diff-index --name-only "$(cg-object-id -t $head)" >>"$statedir/commit-ignore"
 235 # Don't keep around useless empty files
 236 [ -s "$statedir/commit-ignore" ] || rm "$statedir/commit-ignore"
 237
 238 if ! git-read-tree -u -m "$(cg-object-id -t "$base")" "$(cg-object-id -t "$head")" "$(cg-object-id -t "$branch")"; then
 239         echo "cg-merge: git-read-tree failed (merge likely blocked by local changes)" >&2
 240         posthook "$mergetype" localchanges
 241         rm -f "$statedir/commit-ignore"
 242         rmdir "$statedir"
 243         exit 1
 244 fi
 245
 246 echo "$base" >>"$statedir/merge-base"
 247 echo "$branch" >>"$statedir/merging"
 248 echo "$branchname" >>"$statedir/merging-sym"
 249 [ "$squash" ] && echo "$branch" >>"$statedir/squashing"
 250
 251 if ! git-merge-index -o -q "${COGITO_LIB}"cg-Xmergefile -a || [ "$careful" ]; then
 252         echo >&2
 253         if [ ! "$careful" ]; then
 254                 echo "  Conflicts during merge. Do cg-commit after resolving them." >&2
 255         else
 256                 echo "  Do cg-commit after reviewing the merge." >&2
 257         fi
 258         if [ -s "$statedir/commit-ignore" ]; then
 259                 echo "  cg-reset will cancel the merge (but also your pending local changes!)." >&2
 260                 echo >&2
 261                 echo "  These files contained local modifications and won't be automatically chosen for committing:" >&2
 262                 cat "$statedir/commit-ignore" >&2
 263         else
 264                 echo "  cg-reset will cancel the merge." >&2
 265                 echo >&2
 266         fi
 267         posthook "$mergetype" conflicts
 268         exit 2
 269 fi
 270
 271 echo
 272 readtree=
 273 if ! cg-commit -C; then
 274         readtree=1
 275         echo "cg-merge: COMMIT FAILED, retry manually" >&2
 276         if [ -s "$statedir/commit-ignore" ]; then
 277                 echo "  cg-reset will cancel the merge (but also your pending local changes!)." >&2
 278         else
 279                 echo "  cg-reset will cancel the merge." >&2
 280         fi
 281         posthook "$mergetype" nocommit
 282 fi
 283
 284 [ "$readtree" ] && git-read-tree -m HEAD
 285 # update_index here is safe because no tree<->index desyncs could've
 286 # survived the read-tree above
 287 update_index
 288
 289 posthook "$mergetype" ok