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Junio C Hamano
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checkout: merge local modifications while switching branches.
 * Instead of going interactive, introduce a command line switch '-m' to allow merging changes when normal two-way merge by read-tree prevents branch switching. * Leave the unmerged stages intact if automerge fails, but reset index entries of cleanly merged paths to that of the new branch, so that "git diff" (not "git diff HEAD") would show the local modifications. * Swap the order of trees in read-tree three-way merge used in the fallback, so that `git diff` to show the conflicts become more natural. * Describe the new option and give more examples in the documentation. Signed-off-by: Junio C Hamano <[email protected]>
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‎Documentation/git-checkout.txt

Lines changed: 69 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@ git-checkout - Checkout and switch to a branch.
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SYNOPSIS
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--------
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'git-checkout' [-f] [-b <new_branch>] [<branch>] [<paths>...]
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'git-checkout' [-f] [-b <new_branch>] [-m] [<branch>] [<paths>...]
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DESCRIPTION
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-----------
@@ -34,6 +34,19 @@ OPTIONS
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-b::
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Create a new branch and start it at <branch>.
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-m::
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If you have local modifications to a file that is
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different between the current branch and the branch you
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are switching to, the command refuses to switch
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branches, to preserve your modifications in context.
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With this option, a three-way merge between the current
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branch, your working tree contents, and the new branch
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is done, and you will be on the new branch.
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+
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When a merge conflict happens, the index entries for conflicting
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paths are left unmerged, and you need to resolve the conflicts
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and mark the resolved paths with `git update-index`.
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<new_branch>::
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Name for the new branch.
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@@ -42,13 +55,13 @@ OPTIONS
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commit. Defaults to HEAD.
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EXAMPLE
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-------
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EXAMPLES
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--------
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The following sequence checks out the `master` branch, reverts
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. The following sequence checks out the `master` branch, reverts
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the `Makefile` to two revisions back, deletes hello.c by
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mistake, and gets it back from the index.
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+
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------------
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$ git checkout master <1>
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$ git checkout master~2 Makefile <2>
@@ -59,15 +72,64 @@ $ git checkout hello.c <3>
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<2> take out a file out of other commit
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<3> or "git checkout -- hello.c", as in the next example.
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------------
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+
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If you have an unfortunate branch that is named `hello.c`, the
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last step above would be confused as an instruction to switch to
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that branch. You should instead write:
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+
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------------
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$ git checkout -- hello.c
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------------
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. After working in a wrong branch, switching to the correct
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branch you would want to is done with:
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+
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------------
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$ git checkout mytopic
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------------
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+
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However, your "wrong" branch and correct "mytopic" branch may
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differ in files that you have locally modified, in which case,
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the above checkout would fail like this:
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+
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------------
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$ git checkout mytopic
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fatal: Entry 'frotz' not uptodate. Cannot merge.
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------------
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+
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You can give the `-m` flag to the command, which would try a
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three-way merge:
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+
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------------
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$ git checkout -m mytopic
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Auto-merging frotz
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------------
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+
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After this three-way merge, the local modifications are _not_
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registered in your index file, so `git diff` would show you what
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changes you made since the tip of the new branch.
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. When a merge conflict happens during switching branches with
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the `-m` option, you would see something like this:
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+
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------------
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$ git checkout -m mytopic
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Auto-merging frotz
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merge: warning: conflicts during merge
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ERROR: Merge conflict in frotz
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fatal: merge program failed
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------------
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+
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At this point, `git diff` shows the changes cleanly merged as in
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the previous example, as well as the changes in the conflicted
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files. Edit and resolve the conflict and mark it resolved with
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`git update-index` as usual:
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+
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------------
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$ edit frotz
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$ git update-index frotz
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------------
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Author
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------

‎git-checkout.sh

Lines changed: 38 additions & 22 deletions
Original file line numberDiff line numberDiff line change
@@ -1,6 +1,6 @@
11
#!/bin/sh
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3-
USAGE='[-f] [-b <new_branch>] [<branch>] [<paths>...]'
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USAGE='[-f] [-b <new_branch>] [-m] [<branch>] [<paths>...]'
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SUBDIRECTORY_OK=Sometimes
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. git-sh-setup
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@@ -9,6 +9,7 @@ new=
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force=
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branch=
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newbranch=
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merge=
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while [ "$#" != "0" ]; do
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arg="$1"
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shift
@@ -26,6 +27,9 @@ while [ "$#" != "0" ]; do
2627
"-f")
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force=1
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;;
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-m)
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merge=1
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;;
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--)
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break
3135
;;
@@ -71,7 +75,7 @@ done
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7276
if test "$#" -ge 1
7377
then
74-
if test '' != "$newbranch$force"
78+
if test '' != "$newbranch$force$merge"
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then
7680
die "updating paths and switching branches or forcing are incompatible."
7781
fi
@@ -121,32 +125,44 @@ then
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git-checkout-index -q -f -u -a
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else
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git-update-index --refresh >/dev/null
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git-read-tree -m -u $old $new || (
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echo >&2 -n "Try automerge [y/N]? "
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read yesno
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case "$yesno" in [yY]*) ;; *) exit 1 ;; esac
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# NEEDSWORK: We may want to reset the index from the $new for
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# these paths after the automerge happens, but it is not done
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# yet. Probably we need to leave unmerged ones alone, and
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# yank the object name & mode from $new for cleanly merged
133-
# paths and stuff them in the index.
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135-
names=`git diff-files --name-only`
136-
case "$names" in
137-
'') ;;
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*)
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echo "$names" | git update-index --remove --stdin ;;
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merge_error=$(git-read-tree -m -u $old $new 2>&1) || (
129+
case "$merge" in
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'')
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echo >&2 "$merge_error"
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exit 1 ;;
140133
esac
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# Match the index to the working tree, and do a three-way.
136+
git diff-files --name-only | git update-index --remove --stdin &&
142137
work=`git write-tree` &&
143-
git read-tree -m -u $old $work $new || exit
138+
git read-tree --reset $new &&
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git checkout-index -f -u -q -a &&
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git read-tree -m -u $old $new $work || exit
141+
144142
if result=`git write-tree 2>/dev/null`
145143
then
146-
echo >&2 "Trivially automerged." ;# can this even happen?
147-
exit 0
144+
echo >&2 "Trivially automerged."
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else
146+
git merge-index -o git-merge-one-file -a
148147
fi
149-
git merge-index -o git-merge-one-file -a
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149+
# Do not register the cleanly merged paths in the index yet.
150+
# this is not a real merge before committing, but just carrying
151+
# the working tree changes along.
152+
unmerged=`git ls-files -u`
153+
git read-tree --reset $new
154+
case "$unmerged" in
155+
'') ;;
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*)
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(
158+
z40=0000000000000000000000000000000000000000
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echo "$unmerged" |
160+
sed -e 's/^[0-7]* [0-9a-f]* /'"0 $z40 /"
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echo "$unmerged"
162+
) | git update-index --index-info
163+
;;
164+
esac
165+
exit 0
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)
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fi
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