How to make an existing git branch track a remote branch?

git branch --set-upstream localbranchname remotebranchroot/remotebranchname[/code]

Eg.[/code]

My list of local/remotes:[/code]

[[email protected] supernova-kernel]$ git branch -a

* jan31

master

remotes/origin/HEAD -> origin/master

remotes/origin/UnderVoltVDD_OC

remotes/origin/battery

remotes/origin/jan31

remotes/origin/master

remotes/origin/sense35

remotes/origin/testuv

remotes/origin/vddhavsocuvsysfs[/code]

So, I have to write:
[[email protected] supernova-kernel]$ git branch --set-upstream jan31 origin/jan31

Branch jan31 set up to track remote branch jan31 from origin.[/code]

Following this, we can pull from the remote to get the remote changes to local:
[[email protected] supernova-kernel]$ git pull

Enter passphrase for key '/home/droidzone/.ssh/id_rsa':

Updating fb1198d..e3cc327

Fast-forward

.config | 10 +-

.config.old | 14 +-

.version | 2 +-

System.map |62738 ++++++++++++++++----------------

arch/arm/boot/compressed/piggy.lzma | Bin 1773249 -> 1774507 bytes

arch/arm/kernel/asm-offsets.s | 35 +-

arch/arm/lib/lib.a | Bin 90930 -> 90966 bytes

arch/arm/mach-msm/acpuclock-scorpion.c | 44 +-

arch/arm/mach-msm/avs.c | 30 +-

arch/arm/mach-msm/qdsp6/amrnb_in.c | 302 -

drivers/cpufreq/modules.builtin | 1 +

drivers/modules.builtin | 1 +

drivers/power/ds2784_battery.c | 412 +-

include/config/auto.conf | 7 +-

include/config/kernel.release | 2 +-

include/config/tristate.conf | 1 +

include/generated/autoconf.h | 7 +-

include/generated/compile.h | 8 +-

include/generated/utsrelease.h | 2 +-

kernel/bounds.s | 17 +-

lib/lib.a | Bin 975468 -> 975564 bytes

modules.builtin | 1 +

modules.order | 5 +

usr/.initramfs_data.cpio.d | 2 +-

24 files changed, 31918 insertions(+), 31723 deletions(-)

delete mode 100644 arch/arm/mach-msm/qdsp6/amrnb_in.c

[/code]

Note that sometimes we have to clean the local git and reset it to the last sync state before we can pull.
[[email protected] supernova-kernel]$ git clean

fatal: clean.requireForce defaults to true and neither -n nor -f given; refusing to clean

[[email protected] supernova-kernel]$ git clean -f

Removing .missing-syscalls.d

Not removing drivers/drivers/staging/rt2860/iface/

Removing fs/btrfs/modules.order

Removing fs/ext3/modules.order

Removing fs/fuse/modules.builtin

Removing fs/fuse/modules.order

Removing fs/jbd/modules.order

[[email protected] supernova-kernel]$ git reset[/code]