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2016-03-23merge: refuse to create too cool a merge by defaultLibravatar Junio C Hamano1-1/+1
While it makes sense to allow merging unrelated histories of two projects that started independently into one, in the way "gitk" was merged to "git" itself aka "the coolest merge ever", such a merge is still an unusual event. Worse, if somebody creates an independent history by starting from a tarball of an established project and sends a pull request to the original project, "git merge" however happily creates such a merge without any sign of something unusual is happening. Teach "git merge" to refuse to create such a merge by default, unless the user passes a new "--allow-unrelated-histories" option to tell it that the user is aware that two unrelated projects are merged. Because such a "two project merge" is a rare event, a configuration option to always allow such a merge is not added. We could add the same option to "git pull" and have it passed through to underlying "git merge". I do not have a fundamental opposition against such a feature, but this commit does not do so and instead leaves it as low-hanging fruit for others, because such a "two project merge" would be done after fetching the other project into some location in the working tree of an existing project and making sure how well they fit together, it is sufficient to allow a local merge without such an option pass-through from "git pull" to "git merge". Many tests that are updated by this patch does the pass-through manually by turning: git pull something into its equivalent: git fetch something && git merge --allow-unrelated-histories FETCH_HEAD If somebody is inclined to add such an option, updated tests in this change need to be adjusted back to: git pull --allow-unrelated-histories something Signed-off-by: Junio C Hamano <gitster@pobox.com>
2015-03-20t: assume test_cmp produces verbose outputLibravatar Jeff King1-8/+2
Some tests call test_cmp, and if it fails show the actual output generated. This is mostly pointless, as test_cmp will already show a diff between the expected and actual output. It also fools --chain-lint by putting an "||" in the middle of the chain, so we'd rather not use this construct. Note that these cases actually show a pre-processed version of the data, rather than exactly what test_cmp would show. However, test_cmp's output is generally good for pointing the user in the right direction, and they can then dig in the trash directory themselves if they want to see more details. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-08-01log: use true parents for diff even when rewritingLibravatar Thomas Rast1-0/+6
When using pathspec filtering in combination with diff-based log output, parent simplification happens before the diff is computed. The diff is therefore against the *simplified* parents. This works okay, arguably by accident, in the normal case: simplification reduces to one parent as long as the commit is TREESAME to it. So the simplified parent of any given commit must have the same tree contents on the filtered paths as its true (unfiltered) parent. However, --full-diff breaks this guarantee, and indeed gives pretty spectacular results when comparing the output of git log --graph --stat ... git log --graph --full-diff --stat ... (--graph internally kicks in parent simplification, much like --parents). To fix it, store a copy of the parent list before simplification (in a slab) whenever --full-diff is in effect. Then use the stored parents instead of the simplified ones in the commit display code paths. The latter do not actually check for --full-diff to avoid duplicated code; they just grab the original parents if save_parents() has not been called for this revision walk. For ordinary commits it should be obvious that this is the right thing to do. Merge commits are a bit subtle. Observe that with default simplification, merge simplification is an all-or-nothing decision: either the merge is TREESAME to one parent and disappears, or it is different from all parents and the parent list remains intact. Redundant parents are not pruned, so the existing code also shows them as a merge. So if we do show a merge commit, the parent list just consists of the rewrite result on each parent. Running, e.g., --cc on this in --full-diff mode is not very useful: if any commits were skipped, some hunks will disagree with all sides of the merge (with one side, because commits were skipped; with the others, because they didn't have those changes in the first place). This triggers --cc showing these hunks spuriously. Therefore I believe that even for merge commits it is better to show the diffs wrt. the original parents. Reported-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Helped-by: Junio C Hamano <gitster@pobox.com> Helped-by: Ramsay Jones <ramsay@ramsay1.demon.co.uk> Signed-off-by: Thomas Rast <trast@inf.ethz.ch> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-05-16simplify-merges: drop merge from irrelevant side branchLibravatar Kevin Bracey1-1/+1
Reimplement commit 4b7f53da on top of the new simplify-merges infrastructure, tightening the condition to only consider root parents; the original version incorrectly dropped parents that were TREESAME to anything. Original log message follows. The merge simplification rule stated in 6546b59 (revision traversal: show full history with merge simplification, 2008-07-31) still treated merge commits too specially. Namely, in a history with this shape: ---o---o---M / x---x---x where three 'x' were on a history completely unrelated to the main history 'o' and do not touch any of the paths we are following, we still said that after simplifying all of the parents of M, 'x' (which is the leftmost 'x' that rightmost 'x simplifies down to) and 'o' (which would be the last commit on the main history that touches the paths we are following) are independent from each other, and both need to be kept. That is incorrect; when the side branch 'x' never touches the paths, it should be removed to allow M to simplify down to the last commit on the main history that touches the paths. Suggested-by: Junio C Hamano <gitster@pobox.com> Signed-off-by: Kevin Bracey <kevin@bracey.fi> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-05-16t6012: update test for tweaked full-history traversalLibravatar Junio C Hamano1-6/+23
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-04-08Revert 4b7f53da7618 (simplify-merges: drop merge from irrelevant side ↵Libravatar Junio C Hamano1-3/+9
branch, 2013-01-17) Kevin Bracey reports that the change regresses a case shown in the user manual. Trading one fix with another breakage is not worth it. Just keep the test to document the existing breakage, and revert the change for now. Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-03-28Merge branch 'jc/remove-treesame-parent-in-simplify-merges'Libravatar Junio C Hamano1-5/+21
The --simplify-merges logic did not cull irrelevant parents from a merge that is otherwise not interesting with respect to the paths we are following. This touches a fairly core part of the revision traversal infrastructure; even though I think this change is correct, please report immediately if you find any unintended side effect. * jc/remove-treesame-parent-in-simplify-merges: simplify-merges: drop merge from irrelevant side branch
2013-01-17simplify-merges: drop merge from irrelevant side branchLibravatar Junio C Hamano1-5/+21
The merge simplification rule stated in 6546b59 (revision traversal: show full history with merge simplification, 2008-07-31) still treated merge commits too specially. Namely, in a history with this shape: ---o---o---M / x---x---x where three 'x' were on a history completely unrelated to the main history 'o' and do not touch any of the paths we are following, we still said that after simplifying all of the parents of M, 'x' (which is the leftmost 'x' that rightmost 'x simplifies down to) and 'o' (which would be the last commit on the main history that touches the paths we are following) are independent from each other, and both need to be kept. That is incorrect; when the side branch 'x' never touches the paths, it should be removed to allow M to simplify down to the last commit on the main history that touches the paths. Signed-off-by: Junio C Hamano <gitster@pobox.com>
2012-01-19Making pathspec limited log play nicer with --first-parentLibravatar Junio C Hamano1-0/+1
In a topic branch workflow, you often want to find the latest commit that merged a side branch that touched a particular area of the system, so that a new topic branch to work on that area can be forked from that commit. For example, I wanted to find an appropriate fork-point to queue Luke's changes related to git-p4 in contrib/fast-import/. "git log --first-parent" traverses the first-parent chain, and "-m --stat" shows the list of paths touched by commits including merge commits. We could ask the question this way: # What is the latest commit that touched that path? $ git log --first-parent --oneline -m --stat master | sed -e '/^ contrib\/fast-import\/git-p4 /q' | tail The above finds that 8cbfc11 (Merge branch 'pw/p4-view-updates', 2012-01-06) was such a commit. But a more natural way to spell this question is this: $ git log --first-parent --oneline -m --stat -1 master -- \ contrib/fast-import/git-p4 Unfortunately, this does not work. It finds ecb7cf9 (git-p4: rewrite view handling, 2012-01-02). This commit is a part of the merged topic branch and is _not_ on the first-parent path from the 'master': $ git show-branch 8cbfc11 ecb7cf9 ! [8cbfc11] Merge branch 'pw/p4-view-updates' ! [ecb7cf9] git-p4: rewrite view handling -- - [8cbfc11] Merge branch 'pw/p4-view-updates' + [8cbfc11^2] git-p4: view spec documentation ++ [ecb7cf9] git-p4: rewrite view handling The problem is caused by the merge simplification logic when it inspects the merge commit 8cbfc11. In this case, the history leading to the tip of 'master' did not touch git-p4 since 'pw/p4-view-updates' topic forked, and the result of the merge is simply a copy from the tip of the topic branch in the view limited by the given pathspec. The merge simplification logic discards the history on the mainline side of the merge, and pretends as if the sole parent of the merge is its second parent, i.e. the tip of the topic. While this simplification is correct in the general case, it is at least surprising if not outright wrong when the user explicitly asked to show the first-parent history. Here is an attempt to fix this issue, by not allowing us to compare the merge result with anything but the first parent when --first-parent is in effect, to avoid the history traversal veering off to the side branch. Signed-off-by: Junio C Hamano <gitster@pobox.com>
2010-01-03tests: move convenience regexp to match object names to test-lib.shLibravatar Junio C Hamano1-3/+0
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2008-08-03Topo-sort before --simplify-mergesLibravatar Junio C Hamano1-0/+93
This makes the algorithm more honest about what it is doing. We start from an already limited, topo-sorted list, and postprocess it by simplifying the irrelevant merges away. Signed-off-by: Junio C Hamano <gitster@pobox.com>