Added Packing Heursitics IRC writeup.

diff --git a/git-merge.sh b/git-merge.sh
index cc0952a97db7d998a3f26e98b93cf2154887abd5..78ab422e4ef294d8bcffba91bb7e2116e381d98e 100755 (executable)
--- a/git-merge.sh
+++ b/git-merge.sh
@@ -11,11 +11,15 @@ LF='
 '
 
 all_strategies='recursive octopus resolve stupid ours'
-default_strategies='recursive'
+default_twohead_strategies='recursive'
+default_octopus_strategies='octopus'
+no_trivial_merge_strategies='ours'
 use_strategies=
+
+index_merge=t
 if test "@@NO_PYTHON@@"; then
        all_strategies='resolve octopus stupid ours'
-       default_strategies='resolve'
+       default_twohead_strategies='resolve'
 fi
 
 dropsave() {
@@ -90,8 +94,6 @@ do
        shift
 done
 
-test "$#" -le 2 && usage ;# we need at least two heads.
-
 merge_msg="$1"
 shift
 head_arg="$1"
@@ -99,6 +101,8 @@ head=$(git-rev-parse --verify "$1"^0) || usage
 shift
 
 # All the rest are remote heads
+test "$#" = 0 && usage ;# we need at least one remote head.
+
 remoteheads=
 for remote
 do
@@ -108,6 +112,27 @@ do
 done
 set x $remoteheads ; shift
 
+case "$use_strategies" in
+'')
+       case "$#" in
+       1)
+               use_strategies="$default_twohead_strategies" ;;
+       *)
+               use_strategies="$default_octopus_strategies" ;;
+       esac
+       ;;
+esac
+
+for s in $use_strategies
+do
+       case " $s " in
+       *" $no_trivial_merge_strategies "*)
+               index_merge=f
+               break
+               ;;
+       esac
+done
+
 case "$#" in
 1)
        common=$(git-merge-base --all $head "$@")
@@ -118,18 +143,21 @@ case "$#" in
 esac
 echo "$head" >"$GIT_DIR/ORIG_HEAD"
 
-case "$#,$common,$no_commit" in
-*,'',*)
+case "$index_merge,$#,$common,$no_commit" in
+f,*)
+       # We've been told not to try anything clever.  Skip to real merge.
+       ;;
+?,*,'',*)
        # No common ancestors found. We need a real merge.
        ;;
-1,"$1",*)
+?,1,"$1",*)
        # If head can reach all the merge then we are up to date.
-       # but first the most common case of merging one remote
+       # but first the most common case of merging one remote.
        echo "Already up-to-date."
        dropsave
        exit 0
        ;;
-1,"$head",*)
+?,1,"$head",*)
        # Again the most common case of merging one remote.
        echo "Updating from $head to $1"
        git-update-index --refresh 2>/dev/null
@@ -139,11 +167,11 @@ case "$#,$common,$no_commit" in
        dropsave
        exit 0
        ;;
-1,?*"$LF"?*,*)
+?,1,?*"$LF"?*,*)
        # We are not doing octopus and not fast forward.  Need a
        # real merge.
        ;;
-1,*,)
+?,1,*,)
        # We are not doing octopus, not fast forward, and have only
        # one common.  See if it is really trivial.
        git var GIT_COMMITTER_IDENT >/dev/null || exit
@@ -188,17 +216,6 @@ esac
 # We are going to make a new commit.
 git var GIT_COMMITTER_IDENT >/dev/null || exit
 
-case "$use_strategies" in
-'')
-       case "$#" in
-       1)
-               use_strategies="$default_strategies" ;;
-       *)
-               use_strategies=octopus ;;
-       esac            
-       ;;
-esac
-
 # At this point, we need a real merge.  No matter what strategy
 # we use, it would operate on the index, possibly affecting the
 # working tree, and when resolved cleanly, have the desired tree
@@ -270,11 +287,7 @@ done
 # auto resolved the merge cleanly.
 if test '' != "$result_tree"
 then
-    parents="-p $head"
-    for remote
-    do
-        parents="$parents -p $remote"
-    done
+    parents=$(git-show-branch --independent "$head" "$@" | sed -e 's/^/-p /')
     result_commit=$(echo "$merge_msg" | git-commit-tree $result_tree $parents) || exit
     finish "$result_commit" "Merge $result_commit, made by $wt_strategy."
     dropsave