Re: Find out on which branch a commit was originally made

From: Artur Skawina <art.08.09@gmail.com>
Date: Sep 20, 2010, 15:49 UTC
Message-ID: <4C9782A3.5010005@gmail.com>
In-Reply-To: <4C973E5B.4090201@gmail.com>

On 09/20/10 12:58, Artur Skawina wrote:

Show 37 quoted lines

> On 09/20/10 10:12, Stefan Haller wrote:
>> Seth Robertson <in-gitvger@baka.org> wrote:
> 
>>>          -AA-- subtopic
>>>         /     \
>>>        A---B---C topic
>>>       /         \
>>>  D---E---F---G---H---I---J---K---L---M---N master
>>>                           \         /
>>>                            O---P---Q another-topic
>>>
>>>
>>> In the above example, the subtopic branch merge from AA to C prevents
>>> you from finding out what branch B is on using the original script.
>>
>> When you say "the original script", are you talking about Artur's
>> one-liner or my script?
>>
>> My script gives me exactly the information I want in all cases.  For a
>> given command $1 and a target branch $2, it shows you all merges that
>> were involved in bringing $1 into $2. For example:
>>
>>   Called with "B" "master", it returns H
> 
> No, it will return both C and H, just like my one-liner; this will be
> misleading, the user won't be able to figure out where 'B" came from
> w/o looking at the graph, from output like:
> 
> $ git-show-merges-since B master
> C..... Merge branch 'subtopic' into topic
> H..... Merge branch 'topic'
> 
> The results for 'B' and 'AA' will be exactly the same.
> 
> For 'B', the 'C' merge should be omitted; skipping it because 'B'
> comes in via first parent would probably work, but i can't turn that
> into a one-liner right now...

Yeah, that was it; the script below will correctly handle not only the simple example above, but also some real cases.

Usage: git-find-branch-for <rev> [long-lived-branch]

Returns some merge commits, making it easier to find out from which branch a change originated. Returns nothing if it did not find an interesting merge all the way up to long-lived-branch (which defaults to "master")

Example, using git.git:

$ time ../../../stefans-script bac80370817 4fa088209c81845e73756a4173a8c954e25958d2 Merge branch 'jk/run-command-use-shell' 225f78c817755bebff91629cc525a258cf60eaea Merge branch 'master' of git://repo.or.cz/alt-git into jn/autodep 037c43c68e220739e690540de89a6d5835fefe73 Merge remote branch 'ko/master' into jc/read-tree-cache-tree-fix 1m23.271s user 0m2.173s system 1m26.389s elapsed 98.90% CPU

$ time ../../../git-find-branch-for bac80370817 4fa08820 Merge branch 'jk/run-command-use-shell' * jk/run-command-use 1263743895 225f78c8 Merge branch 'master' of git://repo.or.cz/alt-git into jn/autodep 1264500524 037c43c6 Merge remote branch 'ko/master' into jc/read-tree-cache-tree-fix 1278615350 0m0.270s user 0m0.017s system 0m0.287s elapsed 99.87% CPU $

So it's also a little bit faster. Received very little testing, i only tried it on a few commits, other than the example from this thread, but so far seems to do the right thing for all of them. Unpikifying is left as an exercise for the user. ;)

artur

------------------------------------------------------------------------------ #! /usr/bin/env pike // git-find-branch-for <rev> [long-lived-branch] // Probably needs pike7.8 #define die(a...) exit(1, "Aborting; %s"+a)

string run(string ... cmdline) {
   mapping r;
   mixed e = catch { r = Process.run( ({@cmdline}) ); };
   if (e || r["exitcode"])
      die("", e?e:r["stderr"]);
   return r["stdout"];
}

mapping commits = ([]);

array parsecommits(string from, string to) {
   array res = ({});
   string id;
   string gitout = run("git", "rev-list", "--format=raw",  "--ancestry-path",
                                          "--date-order", from+".."+to);
   array lines = gitout/"\n";

   foreach (lines, string line) {
      array words = line/" ";
      if (words[0]=="commit") {
         id = words[1][0]!='-' ? words[1] : words[1][1..];
	 commits[id] = ([]);
	 res += ({id});
      }
      commits[id][words[0]] += words[1..];
   }
   return res;
}

int ismerge(string id) {
   return commits[id]["parent"] && sizeof(commits[id]["parent"])>1;
}

mapping desc = ([]);

int main(int argc, array argv) {
   argv[1] = (run("git", "rev-parse", argv[1])/"\n")[0];
   if (argc==2)
      argv += ({"master"});
   argv[2] = (run("git", "rev-parse", argv[2])/"\n")[0];
   array merges = parsecommits(argv[1], argv[2]);
   merges = reverse(merges);
   desc[argv[1]] = 1;
   foreach (merges, string id) {
      if (commits[id]["parent"])
         foreach (commits[id]["parent"], string parent)
            if (desc[parent])
        	desc[id] = 1;
      if (ismerge(id))
         if (!desc[commits[id]["parent"][0]]) {
	    int comtime = (int)commits[id]["committer"][-2];
	    comtime += (int)commits[id]["committer"][-1]/100*60*60;
            write("%.8s %.70s %d\n", id, commits[id][""]*" ", comtime );
	 }
   }
}
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