push - Pushing git subtree changes to upstream repository fails -

i'm trying ensure git's subtrees work me before incorporate project. encountered problem when pushing subtree changes upstream repository.

the setup have 2 repos, sub , main, , main includes sub repo subtree.

then following:

1. initialize both repos initial commit.
2. update sub repo directly (i.e. outside of main).
3. update sub repo within main repo.
4. split changes sub (using git subtree split) separate branch, checkout.
5. attempt push upstream sub repo. naturally, push rejected because lose direct update sub.
6. pull new change sub repo.
7. attempt push upstream sub repo. time, should work, doesn't.

i've written script encapsulates problem. i'm using git version 1.8.2.1 subtree module enabled. here's script:

#!/bin/bash  echo -n "wiping old repositories..." rm -rf main sub sub-home echo "done"  echo -n "initializing main , sub repositories..." mkdir sub-home ( cd sub-home ; git init -q --bare ) git clone sub-home sub > /dev/null 2>&1 ( cd sub ; echo subfile > subfile ; git add subfile ;   git commit -qm "adding root-level file sub-project" ;   git push -q origin master ) mkdir main ( cd main ; git init -q ; echo file > file ; git add file ;   git commit -qm "adding root-level file main-project" ) echo "done"  echo -n "adding sub project subtree main project..." wd=$pwd ( cd main ; git remote add sub-remote file://$wd/sub-home ;   git subtree add -p sub sub-remote master >/dev/null 2>&1 ) echo "done"  echo -n "committing sub-project directly..." ( cd sub ; date > the-date ; git add the-date ;   git commit -qm "adding the-date sub-project"   git push -q origin master ) echo "done"  echo -n "committing sub-project within main project..." ( cd main ; echo 'subfile what?' > sub/subfile ; git add sub/subfile ;   git commit -qm "changing sub-project within main project" ) echo "done"  cd main git subtree split -q -p sub -b split-branch >/dev/null git checkout -q split-branch echo -e "\npushing main subtree sub project, should fail:" git push sub-remote master echo -e "\nbut if pull first..." git pull -q --no-edit sub-remote master echo "...then push *should* work (but doesn't):" git push sub-remote master cd .. 

and here's output:

$ ./test.sh wiping old repositories...done initializing main , sub repositories...done adding sub project subtree main project...done committing sub-project directly...done committing sub-project within main project...done  pushing main subtree sub project, should fail: file:///tmp/git/sub-home  ! [rejected]        master -> master (fetch first) error: failed push refs 'file:///tmp/git/sub-home' hint: updates rejected because remote contains work hint: not have locally. caused repository pushing hint: same ref. may want first merge remote changes (e.g., hint: 'git pull') before pushing again. hint: see 'note fast-forwards' in 'git push --help' details.  if pull first... ...then push *should* work (but doesn't): file:///tmp/git/sub-home  ! [rejected]        master -> master (non-fast-forward) error: failed push refs 'file:///tmp/git/sub-home' hint: updates rejected because pushed branch tip behind remote hint: counterpart. check out branch , merge remote changes hint: (e.g. 'git pull') before pushing again. hint: see 'note fast-forwards' in 'git push --help' details. 

further git pull commands (from split-branch branch of main) "already up-to-date".

the thing that's confusing me that, far can tell, git push command should giving upstream repo fast-forward commit, demonstrated following git log output:

$ ( cd main ; git log ) commit 357fe9fb42f5d122338940eb4f22d3ca9d276318 merge: 472904f cb5d1d3 author: jeff terrell <jeff.terrell@acm.org> date:   fri apr 19 16:03:03 2013 -0400      merge branch 'master' of file:///tmp/git/sub-home split-branch  commit 472904f432c3a0a89acde02691b8281ac5246fd1 author: jeff terrell <jeff.terrell@acm.org> date:   fri apr 19 16:03:02 2013 -0400      changing sub-project within main project  commit cb5d1d34ce56374f78c98c5b3f3daa314907b62d author: jeff terrell <jeff.terrell@acm.org> date:   fri apr 19 16:03:02 2013 -0400      adding the-date sub-project  commit 7d1942203d30e0d9e8663517e6d594545bc50640 author: jeff terrell <jeff.terrell@acm.org> date:   fri apr 19 16:03:02 2013 -0400      adding root-level file sub-project $ (cd sub ; git log ) commit cb5d1d34ce56374f78c98c5b3f3daa314907b62d author: jeff terrell <jeff.terrell@acm.org> date:   fri apr 19 16:03:02 2013 -0400      adding the-date sub-project  commit 7d1942203d30e0d9e8663517e6d594545bc50640 author: jeff terrell <jeff.terrell@acm.org> date:   fri apr 19 16:03:02 2013 -0400      adding root-level file sub-project 

here questions (finally):

1. why push rejected?
2. what can it? (if using --force option answer, how can not doing destructive?)
3. is there better way use subtree module avoid problem? (note: i'm not willing use submodules.)

your problem not related git subtree. having problems old tricky git ui. in case git push. assumed syntax follows git pull. rather naive – using git ;).

you push output tells wrong here:

to file:///tmp/git/sub-home ! [rejected]        master -> master (non-fast-forward) 

git pull sub-remote master fetches , merges head of sub-remote/master checked-out branch, expected. git push sub-remote master not push head of checked-out branch sub-remote/master. push branch of same name. in case master, can see in output above.

from git push (syntax git push <repsitory> <refspec>):

the format of <refspec> parameter optional plus +, followed source ref <src>, followed colon :, followed destination ref <dst>. used specify <src> object <dst> ref in remote repository updated.

the <dst> tells ref on remote side updated push. arbitrary expressions cannot used here, actual ref must named. if :<dst> omitted, same ref <src> updated.

so command looking git push sub-remote splitbranch:master. why not using git subtree push in first place?