Abstract
We consider the problem of merging individual text documents, motivated by the single-file merge algorithms of document-based version control systems. Abstracting away the merging of conflicting edits to an external conflict resolution function (possibly implemented by a human), we consider the efficient identification of conflicting regions. We show how to implement tree-based document representation to quickly answer a data structure inspired by the “blame” query of some version control systems. A “blame” query associates every line of a document with the revision in which it was last edited. Our tree uses this idea to quickly identify conflicting edits. We show how to perform a merge operation in time proportional to the sum of the logarithms of the shared regions of the documents, plus the cost of conflict resolution. Our data structure is functional and therefore confluently persistent, allowing arbitrary version DAGs as in real version-control systems. Our results rely on concurrent traversal of two trees with short circuiting when shared subtrees are encountered.
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References
Bender, M.A., Cole, R., Demaine, E.D., Farach-Colton, M., Zito, J.: Two simplified algorithms for maintaining order in a list. In: Möhring, R.H., Raman, R. (eds.) ESA 2002. LNCS, vol. 2461, pp. 152–164. Springer, Heidelberg (2002)
Carlsson, S., Levcopoulos, C., Petersson, O.: Sublinear merging and natural mergesort. Algorithmica 9, 629–648 (1993)
Cohen, B.: Git can’t be made consistent (April 2011), http://bramcohen.livejournal.com/74462.html
Demaine, E.D., Langerman, S., Price, E.: Confluently persistent tries for efficient version control. Algorithmica 57(3), 462–483 (2010)
Demaine, E.D., López-Ortiz, A., Munro, J.I.: Adaptive set intersections, unions, and differences. In: Proceedings of the 11th Annual ACM-SIAM Symposium on Discrete Algorithms, San Francisco, California, pp. 743–752 (January 2000)
Dietz, P.F., Sleator, D.D.: Two algorithms for maintaining order in a list. In: Proceedings of the 19th Annual ACM Symposium on Theory of Computing, New York City, pp. 365–372 (May 1987)
Driscoll, J.R., Sarnak, N., Sleator, D.D., Tarjan, R.E.: Making data structures persistent. Journal of Computer and System Sciences 38(1), 86–124 (1989)
Fiat, A., Kaplan, H.: Making data structures confluently persistent. In: Proceedings of the 12th Annual Symposium on Discrete Algorithms, Washington, DC, pp. 537–546 (January 2001)
Hudson, G.: Notes on keeping version histories of files (October 2002), http://web.mit.edu/ghudson/thoughts/file-versioning
Mehlhorn, K.: Data Structures and Algorithms. Sorting and Searching, vol. 1, pp. 240–241. Springer (1984)
Moffat, A., Petersson, O., Wormald, N.C.: A tree-based Mergesort. Acta Informatica 35(9), 775–793 (1998)
Okasaki, C.: Purely functional data structures. Cambridge University Press, New York (1998)
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Demaine, E.D., Panchekha, P., Wilson, D.A., Yang, E.Z. (2013). Blame Trees. In: Dehne, F., Solis-Oba, R., Sack, JR. (eds) Algorithms and Data Structures. WADS 2013. Lecture Notes in Computer Science, vol 8037. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-40104-6_25
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DOI: https://doi.org/10.1007/978-3-642-40104-6_25
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