[WIP]Developers only - a different way of creating flashables.. - HTC Amaze 4G

This is NOT going to contain anything for users to flash - this is for developers(or those who aspire and want to learn). This is a work in progress.
I want to make it clear that XDA nor the mods endorse or approve of this thread(well, they are allowing me to post it), but this is a concept that may be helpful for multiple reasons.
Please go easy on me, constructive criticism is welcomed, flaming is not. Do not post if you are not adding to the discussion or a developer asking a question. This is something I have been working on for a "rom" I will be putting out in a few days.. I just decided I would share the process, maybe others can help refine it.
Benefits:
If you build for multiple devices you can use this SAME flashable on those other devices and only need to edit the updater-script, prop edits that are device specific, and any system or apk's that are device specific! This could take 5 minutes or less to change AND upload!
It will work on ANY rom(for the same device) as long as you aren't modifying the things that rom specifically needs - and with this method it would be very rare that you would somehow break a rom.
You can still add files/apks, delete files you don't want, modify(rather than replace) the build.prop - technically you could create a flashable that turns stock into CM9 if you wanted to, but only then is a full ROM really needed.
Users can choose the rom they want and add your customizations(the entire community can use your flashable, rather than just a portion!)
It reduces the flashable filesize - rather than 100-400mb your flashable could be 4-20(depending how much you are changing).
It takes MUCH less time to flash, the recovery log will be shorter/easier to read, and it reduces the chance of errors(you are changing less).
Easier to track the changes since the flashable has been reduced to what is NEEDED.
This is an open source community - other devs and even users could look at your flashable and clearly see what you've done, how you've done it, so everyone benefits.
Easier to support - to make changes is EASY, faster zipping, signing, updating, uploading, etc.
You can choose to make it CONFIGURABLE - add #comments in the updater-script, the included build.prop script, or add a readme in the flashable that tells them what they can remove if they don't want it!
I'm quite sure there are MANY more reasons this is beneficial, but I'll leave it to you to decide..
Post 1 - Benefits, explanation, reasoning
Post 2 - Instructions and a soon a flashable example that I will publish
Post 3 = profit?!
First, there are totally different systems out there we can try to get running, CM9, MIUI, etc- this is when the very framework is absolutely different-- otherwise every rom we have RIGHT NOW is just a series of tweaks to the stock(like the leaked ICS) rom. We can argue that people just tweak what is there, or "develop" something new, but nearly everything is building on the concepts of something before- so let's do it right.
What makes a rom unique:
It is easier to keep track of changes(the /system will only have the changes you make, your updater-script will show you other changes, and any scripts you create will show the last changes) - so there shouldn't be "and other stuff I don't remember" in your changelog. This will also assure that there are less potential issues- you are ONLY changing specific things- troubleshooting these things are easier when you aren't including the entire modified flashable.
What you are trying to accomplish:
The main thing that makes a "rom" stand out from any other is the changes to the build.prop - you totally replaced it with something that is your own(or an adapted version hopefully giving proper credit to whoever's tweaks you are using): but they are using your "rom" if they have your build.prop and not someone else's. Everything else is deleting, copying, setting permissions, etc.
The goal: making it more open source
Until you build something totally new(Cm9, miui, etc), you are working with an open source platform, modifying, adding, deleting, scripting. Period. Admit that you are giving the base platform some tweaks, or a "flavor" that others will hopefully prefer.
If you are already developing, you know that with the correct updater-script you can add apks, delete what you don't want, over-write the things you want to replace- this includes theming and everything else you could want.. and usually you would include this in the full base rom, totally pre-configured. With a build.prop that is yours alone.
Conclusion:
Unless you are building an OS from scratch, or modifying it so heavily that it is more yours than it is not, giving the end users these options without wiping is the way to go. If they can flash your mods and then mine and end up with a better final product, how can this go wrong? This is open source, this is android, this is evolution.

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Instructions:
First, keep track of all the changes you want to make - the better organized you are, the easier this will be. If you aren't even sure what all you did..
How to do it:
One of the main things you are changing by creating a total prepacked rom is the build.prop- perhaps you have tweak A, and I have tweak B, and those tweaks are different enough to change the users experience.. but why not combine them if possible? It IS possible.
Decide on the build.prop edits that you want to add/modify(you will NOT replace their build.prop) and modify the propEditor script as needed - if you build for multiple devices I would recommend you add the device specific ones at the end(with #comments) for easy modification/removal from script. You really only need to MODIFY the RO.whatever lines(because they are read only), everything else can be added to a local.prop in the /data folder
Create your updater-script as you normally would, as you know this does the main work - this will likely remain mostly the same, with just a few lines added for the scripts you need to modify the build.prop. Just make sure you delete what you would from the rom itself with the script
Rather than copy your /system /data or any other files into the rom you would normally be modifying, those are the only files you will include in the flashable - if this is done right it will make all of the changes you want without breaking anything.
If you want others to be able to understand/build upon your work you can add #comments or a readme in the above steps, then all users would have to do is remove the lines you instructed, re-zip(no need to sign if they use 7-zip or winrar) and then flash.
As said in the previous area, outside the build.prop you can make a small flashable that will change everything, but if you can MODIFY tweaks already in the build.prop, or add lines if they don't exist-- we would be creating a continual evolution of a better and better performing rom.. with feedback bad tweaks would get tossed, each developer adds their flavor, but users can flash what they want to get the performance they desire without the headache and confusion that comes with wiping everything of the developer they used before that. This will enable them to learn more about how and what we are doing with their devices, and they can provide feedback that makes it better for everyone.
The code(that may need work) to modify or add lines in the default build.prop is here:
(This may require testing, big thanks to tommytomatoe for all the help, original thread is here.)
Code:
#!/sbin/sh
# Build.prop editor script with basic sed commands
# tommytomatoe
# May 12, 2012
# mounting system as rw
busybox mount -o remount,rw /system
if [ $? != 0 ] ; then exit
fi
FILE=/system/build.prop
TMPFILE=$FILE.tmp
line1=ro.product.version
line2=ro.HOME_APP_ADJ
line3=ro.media.enc.jpeg.quality
#Add more line# formatted as above as needed to identify each prop
line1Arg=Classicv0.1.0
line2Arg=1
line3Arg=100
#Add more line$Arg formatted as above as needed for each prop change
lineNum=
#to add additional prop changes copy the lines between here
prop=$line1
arg=$line1Arg
if grep -Fq $prop $FILE ; then
lineNum=`sed -n "/${prop}/=" $FILE`
echo $lineNum
sed -i "${lineNum} c${prop}=${arg}" $FILE
else
echo "$prop does not exist in build.prop"
echo "appending to end of build.prop"
echo $prop=$arg >> build.prop
fi
#and here and paste to the end, changing the $line# and $line#Arg to match what you've added
# to iterate over all the prop values you want to change,
# just copy and paste the code chunk or create a for loop.
# I will leave it to you to create a for loop
prop=$line2
arg=$line2Arg
if grep -Fq $prop $FILE ; then
lineNum=`sed -n "/${prop}/=" $FILE`
echo $lineNum
sed -i "${lineNum} c${prop}=${arg}" $FILE
else
echo "$prop does not exist in build.prop"
echo "appending to end of build.prop"
echo $prop=$arg >> build.prop
fi
prop=$line3
arg=$line3Arg
if grep -Fq $prop $FILE ; then
lineNum=`sed -n "/${prop}/=" $FILE`
echo $lineNum
sed -i "${lineNum} c${prop}=${arg}" $FILE
else
echo "$prop does not exist in build.prop"
echo "appending to end of build.prop"
echo $prop=$arg >> build.prop
fi
It may require some work, feel free to offer advice if you can help make it better), but you can make a few changes to that, and rather than replacing the entire system on a users phone, you are making YOUR modifications to make their device work better! Read the #comments above to see the different tweaks you are trying to make, and it will automatically either change the value, or it will add the line if it doesn't already exist in the build.prop

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Profit?!
I understand many developers may think this would make it easier to "steal" your work, but as I said before, everything android is open source. Besides, with enough changes this makes it a TRUE rom, and it will be NEARLY as complex as the much larger file he would be uploading.
It could actually be profitable time/effort wise, ANY rom could be done with this as long as you tell them what base to work with.
Example of "profit"
Mike 1986.'s ARHD is on 10 devices, if you check, most of the features in one are in the rest of them. He has enough experience where porting everything over all of his changes to a new rom probably isn't that difficult for him(I'll bet he is VERY organized), but this would enable him to make a few changes to a propEditor script, the updater-script, remove or change out a few files.. re-zip and sign, upload, done.
This also takes out much of the opportunity for developer error or errors during flashing..

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Doubt I'll need it.. but we'll see.