diff options
| -rw-r--r-- | Documentation/technical/api-merge.txt | 70 |
1 files changed, 70 insertions, 0 deletions
diff --git a/Documentation/technical/api-merge.txt b/Documentation/technical/api-merge.txt new file mode 100644 index 0000000..01a89d6 --- /dev/null +++ b/Documentation/technical/api-merge.txt @@ -0,0 +1,70 @@ +merge API +========= + +The merge API helps a program to reconcile two competing sets of +improvements to some files (e.g., unregistered changes from the work +tree versus changes involved in switching to a new branch), reporting +conflicts if found. The library called through this API is +responsible for a few things. + + * determining which trees to merge (recursive ancestor consolidation); + + * lining up corresponding files in the trees to be merged (rename + detection, subtree shifting), reporting edge cases like add/add + and rename/rename conflicts to the user; + + * performing a three-way merge of corresponding files, taking + path-specific merge drivers (specified in `.gitattributes`) + into account. + +Low-level (single file) merge +----------------------------- + +`ll_merge`:: + + Perform a three-way single-file merge in core. This is + a thin wrapper around `xdl_merge` that takes the path and + any merge backend specified in `.gitattributes` or + `.git/info/attributes` into account. Returns 0 for a + clean merge. + +The caller: + +1. allocates an mmbuffer_t variable for the result; +2. allocates and fills variables with the file's original content + and two modified versions (using `read_mmfile`, for example); +3. calls ll_merge(); +4. reads the output from result_buf.ptr and result_buf.size; +5. releases buffers when finished (free(ancestor.ptr); free(ours.ptr); + free(theirs.ptr); free(result_buf.ptr);). + +If the modifications do not merge cleanly, `ll_merge` will return a +nonzero value and `result_buf` will generally include a description of +the conflict bracketed by markers such as the traditional `<<<<<<<` +and `>>>>>>>`. + +The `ancestor_label`, `our_label`, and `their_label` parameters are +used to label the different sides of a conflict if the merge driver +supports this. + +The `flag` parameter is a bitfield: + + - The least significant bit indicates whether this is an internal + merge to consolidate ancestors for a recursive merge. + + - The next two bits allow local conflicts to be automatically + resolved in favor of one side or the other (as in 'git merge-file' + `--ours`/`--theirs`/`--union` for 01, 10, and 11, respectively). + +Everything else +--------------- + +Talk about <merge-recursive.h> and merge_file(): + + - merge_trees() to merge with rename detection + - merge_recursive() for ancestor consolidation + - try_merge_command() for other strategies + - conflict format + - merge options + +(Daniel, Miklos, Stephan, JC) |