我有一个主分支“dev”，我基于dev checkout 了一个分支“A”。下面是我采取的步骤：
1.在A上做修改，提交，然后推送并合并到dev。
1.已在服务器上删除。
1.在局部A上做了一些改动。
1.我尝试将本地A推送到服务器。即在分支A上执行git push --force
1.我发现服务器上的dev被我的本地dev强制更新了。
我的问题是，如果我在本地A分支上做了git push --force，为什么dev是由我的本地dev更新的？

# BSDC-587_For_EMC_test has been merged to dev on server, and deleted on server
# Made some modifications and commit 
$ git status

On branch BSDC-587_For_EMC_test
Your branch is ahead of 'dummy-ondemand/dev' by 5 commits.
  (use "git push" to publish your local commits)
Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git checkout -- <file>..." to discard changes in working directory)

    modified:   ../rtos/ssp/app/svc/config/AmbaCamCtrl.c
    modified:   ../rtos/ssp/app/svc/main/AmbaOpModeCtrlTask.c

Untracked files:
  (use "git add <file>..." to include in what will be committed)

    pkg/network_turnkey/source/usr/local/share/script/emc_download.sh
    ../rtos/mcu_image/bsd_mcu.bin

no changes added to commit (use "git add" and/or "git commit -a")

$ git add ../rtos/ssp/app/svc/config/AmbaCamCtrl.c
$ git add ../rtos/ssp/app/svc/main/AmbaOpModeCtrlTask.c
$ git branch

* BSDC-587_For_EMC_test
  dev

$ git commit -m "BSDC-578 add network checking and downloading"

[BSDC-587_For_EMC_test 85f42e7] BSDC-578 add network checking and downloading
 2 files changed, 33 insertions(+), 4 deletions(-)

// Try to push local branch to server, but it seems like git try to push dev branch

$ git push

To ssh://[email protected]/dummy-ondemand/tsdk-code.git
 ! [rejected]        dev -> dev (fetch first)
error: failed to push some refs to 'ssh://[email protected]/dummy-ondemand/tsdk-code.git'
hint: Updates were rejected because the remote contains work that you do
hint: not have locally. This is usually caused by another repository pushing
hint: to the same ref. You may want to first integrate the remote changes
hint: (e.g., 'git pull ...') before pushing again.
hint: See the 'Note about fast-forwards' in 'git push --help' for details.

$ cd ..
$ git pull

remote: Counting objects: 148, done.
remote: Compressing objects: 100% (148/148), done.
remote: Total 148 (delta 132), reused 0 (delta 0)
Receiving objects: 100% (148/148), 157.20 KiB | 0 bytes/s, done.
Resolving deltas: 100% (132/132), completed with 53 local objects.
From ssh://bitbucket.org/dummy-ondemand/tsdk-code
   b2de179..9a75859  dev        -> dummy-ondemand/dev
 * [new branch]      BSDC-592_store_IMSI_to_flash_at_boot -> dummy-ondemand/BSDC-592_store_IMSI_to_flash_at_boot
 + 07459ca...531ec19 BSDC_faster_time_to_first_picture -> dummy-ondemand/BSDC_faster_time_to_first_picture  (forced update)
Auto-merging rtos/ssp/app/svc/main/AmbaOpModeCtrlTask.c
CONFLICT (content): Merge conflict in rtos/ssp/app/svc/main/AmbaOpModeCtrlTask.c
Recorded preimage for 'rtos/ssp/app/svc/main/AmbaOpModeCtrlTask.c'
Automatic merge failed; fix conflicts and then commit the result.

$ git status

On branch BSDC-587_For_EMC_test
Your branch and 'dummy-ondemand/dev' have diverged,
and have 6 and 2 different commits each, respectively.
  (use "git pull" to merge the remote branch into yours)
You have unmerged paths.
  (fix conflicts and run "git commit")

Changes to be committed:

    modified:   rtos/bsp/trailcam/bsp.c
    modified:   rtos/bsp/trailcam/ringbuffer.c
    modified:   rtos/bsp/trailcam/ringbuffer.h
    modified:   rtos/ssp/app/svc/AmbaUserSysCtrl.c

Unmerged paths:
  (use "git add <file>..." to mark resolution)

    both modified:   rtos/ssp/app/svc/main/AmbaOpModeCtrlTask.c

Untracked files:
  (use "git add <file>..." to include in what will be committed)

    ambalink_sdk_4_9/pkg/network_turnkey/source/usr/local/share/script/emc_download.sh
    rtos/mcu_image/bsd_mcu.bin

$ vi rtos/ssp/app/svc/main/AmbaOpModeCtrlTask.c
$ git add rtos/ssp/app/svc/main/AmbaOpModeCtrlTask.c
$ git commit 

Recorded resolution for 'rtos/ssp/app/svc/main/AmbaOpModeCtrlTask.c'.
[BSDC-587_For_EMC_test a46f1b9] Merge branch 'dev' of ssh://bitbucket.org/dummy-ondemand/tsdk-code into BSDC-587_For_EMC_test
ldy2534@ubuntu:~/Project/project_mcu/context/tekdev/tsdk-code$ git status
On branch BSDC-587_For_EMC_test
Your branch is ahead of 'dummy-ondemand/dev' by 7 commits.
  (use "git push" to publish your local commits)
Untracked files:
  (use "git add <file>..." to include in what will be committed)

    ambalink_sdk_4_9/pkg/network_turnkey/source/usr/local/share/script/emc_download.sh
    rtos/mcu_image/bsd_mcu.bin

nothing added to commit but untracked files present (use "git add" to track)

$ git branch

* BSDC-587_For_EMC_test
  dev
ldy2534@ubuntu:~/Project/project_mcu/context/tekdev/tsdk-code$ git rebase dev
First, rewinding head to replay your work on top of it...
Applying: BSDC-587 EMC test wifi working version
Applying: BSDC-587 improve network connection
Applying: BSDC-587 tidy up code
Applying: BSDC-578 add more comments
Applying: BSDC-587 modifications according to review
Applying: Merged in BSDC-510_fix_x_uart_lost_messages (pull request #178)
Applying: Merged in BSDC-587_For_EMC_test (pull request #177)
Using index info to reconstruct a base tree...
M   ambalink_sdk_4_9/pkg/bsd_app/tekipc_projectlink.cpp
M   ambalink_sdk_4_9/pkg/bsd_app/tekipc_projectlink.h
M   ambalink_sdk_4_9/pkg/bsd_app/xsmtp.cpp
M   ambalink_sdk_4_9/pkg/bsd_app/xsmtp.h
M   rtos/bsp/trailcam/devices.h
M   rtos/ssp/app/svc/bsd_app/tekipc_bsd.cpp
M   rtos/ssp/app/svc/bsd_app/tekipc_bsd.h
M   rtos/ssp/app/svc/config/AmbaCamCtrl.c
M   rtos/ssp/app/svc/format/AmbaMovMuxer.c
M   rtos/ssp/app/svc/main/AmbaOpModeCtrlTask.c
M   rtos/ssp/app/svc/main/AmbaPostProc.c
M   rtos/ssp/app/svc/main/AmbaRecTask.c
M   rtos/ssp/app/svc/main/DemoTask.c
M   rtos/ssp/app/svc/main/inc/AmbaPostProc.h
M   rtos/ssp/app/svc/main/inc/AmbaSVC.h
.git/rebase-apply/patch:86: trailing whitespace.
        return false; 
.git/rebase-apply/patch:665: trailing whitespace.
    
.git/rebase-apply/patch:588: new blank line at EOF.
+
.git/rebase-apply/patch:671: new blank line at EOF.
+
warning: 4 lines add whitespace errors.
Falling back to patching base and 3-way merge...
No changes -- Patch already applied.
Applying: BSDC-578 add network checking and downloading

$ tig
$ git status

On branch BSDC-587_For_EMC_test
Your branch and 'dummy-ondemand/dev' have diverged,
and have 7 and 2 different commits each, respectively.
  (use "git pull" to merge the remote branch into yours)
Untracked files:
  (use "git add <file>..." to include in what will be committed)

    ambalink_sdk_4_9/pkg/network_turnkey/source/usr/local/share/script/emc_download.sh
    rtos/mcu_image/bsd_mcu.bin

nothing added to commit but untracked files present (use "git add" to track)

$ git add ambalink_sdk_4_9/pkg/network_turnkey/source/usr/local/share/script/emc_download.sh
$ git commit -m "BSDC-578 add emc_download script"

[BSDC-587_For_EMC_test a0983d0] BSDC-578 add emc_download script
 1 file changed, 5 insertions(+)
 create mode 100755 ambalink_sdk_4_9/pkg/network_turnkey/source/usr/local/share/script/emc_download.sh

$ git push 

To ssh://[email protected]/dummy-ondemand/tsdk-code.git
 ! [rejected]        dev -> dev (non-fast-forward)
error: failed to push some refs to 'ssh://[email protected]/dummy-ondemand/tsdk-code.git'
hint: Updates were rejected because a pushed branch tip is behind its remote
hint: counterpart. Check out this branch and integrate the remote changes
hint: (e.g. 'git pull ...') before pushing again.
hint: See the 'Note about fast-forwards' in 'git push --help' for details.

$ git push --force

Total 0 (delta 0), reused 0 (delta 0)
remote: 
remote: Create pull request for dev:
remote:   https://bitbucket.org/dummy-ondemand/tsdk-code/pull-requests/new?source=dev&t=1
remote: 
To ssh://[email protected]/dummy-ondemand/tsdk-code.git
 + 9a75859...b2de179 dev -> dev (forced update)

$ git branch

* BSDC-587_For_EMC_test
  dev

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