git-merge: Exit with code 2 if no strategy was able to handle the merge.
[git] / git-merge.sh
1 #!/bin/sh
2 #
3 # Copyright (c) 2005 Junio C Hamano
4 #
5
6 . git-sh-setup
7
8 LF='
9 '
10
11 usage () {
12     die "git-merge [-n] [--no-commit] [-s <strategy>]... <merge-message> <head> <remote>+"
13 }
14
15 all_strategies='recursive octopus resolve stupid ours'
16 default_strategies='recursive'
17 use_strategies=
18
19 dropsave() {
20         rm -f -- "$GIT_DIR/MERGE_HEAD" "$GIT_DIR/MERGE_MSG" \
21                  "$GIT_DIR/MERGE_SAVE" || exit 1
22 }
23
24 savestate() {
25         # Stash away any local modifications.
26         git-diff-index -z --name-only $head |
27         cpio -0 -o >"$GIT_DIR/MERGE_SAVE"
28 }
29
30 restorestate() {
31         if test -f "$GIT_DIR/MERGE_SAVE"
32         then
33                 git reset --hard $head
34                 cpio -iuv <"$GIT_DIR/MERGE_SAVE"
35                 git-update-index --refresh >/dev/null
36         fi
37 }
38
39 finish () {
40         test '' = "$2" || echo "$2"
41         case "$merge_msg" in
42         '')
43                 echo "No merge message -- not updating HEAD"
44                 ;;
45         *)
46                 git-update-ref HEAD "$1" "$head" || exit 1
47                 ;;
48         esac
49
50         case "$no_summary" in
51         '')
52                 git-diff-tree -p -M "$head" "$1" |
53                 git-apply --stat --summary
54                 ;;
55         esac
56 }
57
58 while case "$#" in 0) break ;; esac
59 do
60         case "$1" in
61         -n|--n|--no|--no-|--no-s|--no-su|--no-sum|--no-summ|\
62                 --no-summa|--no-summar|--no-summary)
63                 no_summary=t ;;
64         --no-c|--no-co|--no-com|--no-comm|--no-commi|--no-commit)
65                 no_commit=t ;;
66         -s=*|--s=*|--st=*|--str=*|--stra=*|--strat=*|--strate=*|\
67                 --strateg=*|--strategy=*|\
68         -s|--s|--st|--str|--stra|--strat|--strate|--strateg|--strategy)
69                 case "$#,$1" in
70                 *,*=*)
71                         strategy=`expr "$1" : '-[^=]*=\(.*\)'` ;;
72                 1,*)
73                         usage ;;
74                 *)
75                         strategy="$2"
76                         shift ;;
77                 esac
78                 case " $all_strategies " in
79                 *" $strategy "*)
80                         use_strategies="$use_strategies$strategy " ;;
81                 *)
82                         die "available strategies are: $all_strategies" ;;
83                 esac
84                 ;;
85         -*)     usage ;;
86         *)      break ;;
87         esac
88         shift
89 done
90
91 test "$#" -le 2 && usage ;# we need at least two heads.
92
93 merge_msg="$1"
94 shift
95 head_arg="$1"
96 head=$(git-rev-parse --verify "$1"^0) || usage
97 shift
98
99 # All the rest are remote heads
100 for remote
101 do
102         git-rev-parse --verify "$remote"^0 >/dev/null ||
103             die "$remote - not something we can merge"
104 done
105
106 case "$#" in
107 1)
108         common=$(git-merge-base --all $head "$@")
109         ;;
110 *)
111         common=$(git-show-branch --merge-base $head "$@")
112         ;;
113 esac
114 echo "$head" >"$GIT_DIR/ORIG_HEAD"
115
116 case "$#,$common,$no_commit" in
117 *,'',*)
118         # No common ancestors found. We need a real merge.
119         ;;
120 1,"$1",*)
121         # If head can reach all the merge then we are up to date.
122         # but first the most common case of merging one remote
123         echo "Already up-to-date."
124         dropsave
125         exit 0
126         ;;
127 1,"$head",*)
128         # Again the most common case of merging one remote.
129         echo "Updating from $head to $1."
130         git-update-index --refresh 2>/dev/null
131         new_head=$(git-rev-parse --verify "$1^0") &&
132         git-read-tree -u -m $head "$new_head" &&
133         finish "$new_head" "Fast forward"
134         dropsave
135         exit 0
136         ;;
137 1,?*"$LF"?*,*)
138         # We are not doing octopus and not fast forward.  Need a
139         # real merge.
140         ;;
141 1,*,)
142         # We are not doing octopus, not fast forward, and have only
143         # one common.  See if it is really trivial.
144         echo "Trying really trivial in-index merge..."
145         git-update-index --refresh 2>/dev/null
146         if git-read-tree --trivial -m -u $common $head "$1" &&
147            result_tree=$(git-write-tree)
148         then
149             echo "Wonderful."
150             result_commit=$(
151                 echo "$merge_msg" |
152                 git-commit-tree $result_tree -p HEAD -p "$1"
153             ) || exit
154             finish "$result_commit" "In-index merge"
155             dropsave
156             exit 0
157         fi
158         echo "Nope."
159         ;;
160 *)
161         # An octopus.  If we can reach all the remote we are up to date.
162         up_to_date=t
163         for remote
164         do
165                 common_one=$(git-merge-base --all $head $remote)
166                 if test "$common_one" != "$remote"
167                 then
168                         up_to_date=f
169                         break
170                 fi
171         done
172         if test "$up_to_date" = t
173         then
174                 echo "Already up-to-date. Yeeah!"
175                 dropsave
176                 exit 0
177         fi
178         ;;
179 esac
180
181 case "$use_strategies" in
182 '')
183         case "$#" in
184         1)
185                 use_strategies="$default_strategies" ;;
186         *)
187                 use_strategies=octopus ;;
188         esac            
189         ;;
190 esac
191
192 # At this point, we need a real merge.  No matter what strategy
193 # we use, it would operate on the index, possibly affecting the
194 # working tree, and when resolved cleanly, have the desired tree
195 # in the index -- this means that the index must be in sync with
196 # the $head commit.  The strategies are responsible to ensure this.
197
198 case "$use_strategies" in
199 ?*' '?*)
200     # Stash away the local changes so that we can try more than one.
201     savestate
202     single_strategy=no
203     ;;
204 *)
205     rm -f "$GIT_DIR/MERGE_SAVE"
206     single_strategy=yes
207     ;;
208 esac
209
210 result_tree= best_cnt=-1 best_strategy= wt_strategy=
211 for strategy in $use_strategies
212 do
213     test "$wt_strategy" = '' || {
214         echo "Rewinding the tree to pristine..."
215         restorestate
216     }
217     case "$single_strategy" in
218     no)
219         echo "Trying merge strategy $strategy..."
220         ;;
221     esac
222
223     # Remember which strategy left the state in the working tree
224     wt_strategy=$strategy
225
226     git-merge-$strategy $common -- "$head_arg" "$@"
227     exit=$?
228     if test "$no_commit" = t && test "$exit" = 0
229     then
230         exit=1 ;# pretend it left conflicts.
231     fi
232
233     test "$exit" = 0 || {
234
235         # The backend exits with 1 when conflicts are left to be resolved,
236         # with 2 when it does not handle the given merge at all.
237
238         if test "$exit" -eq 1
239         then
240             cnt=`{
241                 git-diff-files --name-only
242                 git-ls-files --unmerged
243             } | wc -l`
244             if test $best_cnt -le 0 -o $cnt -le $best_cnt
245             then
246                 best_strategy=$strategy
247                 best_cnt=$cnt
248             fi
249         fi
250         continue
251     }
252
253     # Automerge succeeded.
254     result_tree=$(git-write-tree) && break
255 done
256
257 # If we have a resulting tree, that means the strategy module
258 # auto resolved the merge cleanly.
259 if test '' != "$result_tree"
260 then
261     parents="-p $head"
262     for remote
263     do
264         parents="$parents -p $remote"
265     done
266     result_commit=$(echo "$merge_msg" | git-commit-tree $result_tree $parents) || exit
267     finish "$result_commit" "Merge $result_commit, made by $wt_strategy."
268     dropsave
269     exit 0
270 fi
271
272 # Pick the result from the best strategy and have the user fix it up.
273 case "$best_strategy" in
274 '')
275         restorestate
276         echo >&2 "No merge strategy handled the merge."
277         exit 2
278         ;;
279 "$wt_strategy")
280         # We already have its result in the working tree.
281         ;;
282 *)
283         echo "Rewinding the tree to pristine..."
284         restorestate
285         echo "Using the $best_strategy to prepare resolving by hand."
286         git-merge-$best_strategy $common -- "$head_arg" "$@"
287         ;;
288 esac
289 for remote
290 do
291         echo $remote
292 done >"$GIT_DIR/MERGE_HEAD"
293 echo $merge_msg >"$GIT_DIR/MERGE_MSG"
294
295 die "Automatic merge failed/prevented; fix up by hand"