Merge branch 'ds/revision-show-pulls'
"git log" learned "--show-pulls" that helps pathspec limited history views; a merge commit that takes the whole change from a side branch, which is normally omitted from the output, is shown in addition to the commits that introduce real changes. * ds/revision-show-pulls: revision: --show-pulls adds helpful merges
This commit is contained in:
Junio C Hamano
commit
9af3a7cb4d
@ -342,6 +342,12 @@ Default mode::
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branches if the end result is the same (i.e. merging branches
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with the same content)
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--show-pulls::
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Include all commits from the default mode, but also any merge
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commits that are not TREESAME to the first parent but are
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TREESAME to a later parent. This mode is helpful for showing
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the merge commits that "first introduced" a change to a branch.
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--full-history::
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Same as the default mode, but does not prune some history.
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@ -534,7 +540,7 @@ Note the major differences in `N`, `P`, and `Q` over `--full-history`:
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parent and is TREESAME.
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--
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Finally, there is a fifth simplification mode available:
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There is another simplification mode available:
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--ancestry-path::
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Limit the displayed commits to those directly on the ancestry
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@ -573,6 +579,132 @@ option does. Applied to the 'D..M' range, it results in:
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L--M
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-----------------------------------------------------------------------
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Before discussing another option, `--show-pulls`, we need to
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create a new example history.
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+
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A common problem users face when looking at simplified history is that a
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commit they know changed a file somehow does not appear in the file's
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simplified history. Let's demonstrate a new example and show how options
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such as `--full-history` and `--simplify-merges` works in that case:
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+
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-----------------------------------------------------------------------
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.-A---M-----C--N---O---P
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/ / \ \ \/ / /
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I B \ R-'`-Z' /
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\ / \/ /
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\ / /\ /
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`---X--' `---Y--'
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-----------------------------------------------------------------------
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+
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For this example, suppose `I` created `file.txt` which was modified by
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`A`, `B`, and `X` in different ways. The single-parent commits `C`, `Z`,
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and `Y` do not change `file.txt`. The merge commit `M` was created by
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resolving the merge conflict to include both changes from `A` and `B`
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and hence is not TREESAME to either. The merge commit `R`, however, was
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created by ignoring the contents of `file.txt` at `M` and taking only
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the contents of `file.txt` at `X`. Hence, `R` is TREESAME to `X` but not
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`M`. Finally, the natural merge resolution to create `N` is to take the
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contents of `file.txt` at `R`, so `N` is TREESAME to `R` but not `C`.
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The merge commits `O` and `P` are TREESAME to their first parents, but
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not to their second parents, `Z` and `Y` respectively.
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+
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When using the default mode, `N` and `R` both have a TREESAME parent, so
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those edges are walked and the others are ignored. The resulting history
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graph is:
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+
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-----------------------------------------------------------------------
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I---X
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-----------------------------------------------------------------------
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+
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When using `--full-history`, Git walks every edge. This will discover
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the commits `A` and `B` and the merge `M`, but also will reveal the
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merge commits `O` and `P`. With parent rewriting, the resulting graph is:
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+
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-----------------------------------------------------------------------
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.-A---M--------N---O---P
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/ / \ \ \/ / /
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I B \ R-'`--' /
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\ / \/ /
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\ / /\ /
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`---X--' `------'
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-----------------------------------------------------------------------
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+
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Here, the merge commits `O` and `P` contribute extra noise, as they did
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not actually contribute a change to `file.txt`. They only merged a topic
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that was based on an older version of `file.txt`. This is a common
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issue in repositories using a workflow where many contributors work in
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parallel and merge their topic branches along a single trunk: manu
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unrelated merges appear in the `--full-history` results.
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+
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When using the `--simplify-merges` option, the commits `O` and `P`
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disappear from the results. This is because the rewritten second parents
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of `O` and `P` are reachable from their first parents. Those edges are
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removed and then the commits look like single-parent commits that are
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TREESAME to their parent. This also happens to the commit `N`, resulting
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in a history view as follows:
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+
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-----------------------------------------------------------------------
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.-A---M--.
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/ / \
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I B R
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\ / /
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\ / /
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`---X--'
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-----------------------------------------------------------------------
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+
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In this view, we see all of the important single-parent changes from
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`A`, `B`, and `X`. We also see the carefully-resolved merge `M` and the
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not-so-carefully-resolved merge `R`. This is usually enough information
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to determine why the commits `A` and `B` "disappeared" from history in
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the default view. However, there are a few issues with this approach.
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+
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The first issue is performance. Unlike any previous option, the
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`--simplify-merges` option requires walking the entire commit history
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before returning a single result. This can make the option difficult to
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use for very large repositories.
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+
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The second issue is one of auditing. When many contributors are working
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on the same repository, it is important which merge commits introduced
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a change into an important branch. The problematic merge `R` above is
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not likely to be the merge commit that was used to merge into an
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important branch. Instead, the merge `N` was used to merge `R` and `X`
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into the important branch. This commit may have information about why
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the change `X` came to override the changes from `A` and `B` in its
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commit message.
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+
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The `--show-pulls` option helps with both of these issues by adding more
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merge commits to the history results. If a merge is not TREESAME to its
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first parent but is TREESAME to a later parent, then that merge is
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treated as if it "pulled" the change from another branch. When using
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`--show-pulls` on this example (and no other options) the resulting
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graph is:
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+
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-----------------------------------------------------------------------
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I---X---R---N
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-----------------------------------------------------------------------
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+
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Here, the merge commits `R` and `N` are included because they pulled
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the commits `X` and `R` into the base branch, respectively. These
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merges are the reason the commits `A` and `B` do not appear in the
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default history.
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+
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When `--show-pulls` is paired with `--simplify-merges`, the
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graph includes all of the necessary information:
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+
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-----------------------------------------------------------------------
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.-A---M--. N
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/ / \ /
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I B R
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\ / /
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\ / /
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`---X--'
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-----------------------------------------------------------------------
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+
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Notice that since `M` is reachable from `R`, the edge from `N` to `M`
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was simplified away. However, `N` still appears in the history as an
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important commit because it "pulled" the change `R` into the main
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branch.
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The `--simplify-by-decoration` option allows you to view only the
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big picture of the topology of the history, by omitting commits
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that are not referenced by tags. Commits are marked as !TREESAME
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2
object.h
2
object.h
@ -59,7 +59,7 @@ struct object_array {
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/*
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* object flag allocation:
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* revision.h: 0---------10 25----28
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* revision.h: 0---------10 15 25----28
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* fetch-pack.c: 01
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* negotiator/default.c: 2--5
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* walker.c: 0-2
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27
revision.c
27
revision.c
@ -870,7 +870,19 @@ static void try_to_simplify_commit(struct rev_info *revs, struct commit *commit)
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}
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parent->next = NULL;
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commit->parents = parent;
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commit->object.flags |= TREESAME;
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/*
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* A merge commit is a "diversion" if it is not
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* TREESAME to its first parent but is TREESAME
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* to a later parent. In the simplified history,
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* we "divert" the history walk to the later
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* parent. These commits are shown when "show_pulls"
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* is enabled, so do not mark the object as
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* TREESAME here.
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*/
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if (!revs->show_pulls || !nth_parent)
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commit->object.flags |= TREESAME;
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return;
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case REV_TREE_NEW:
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@ -897,6 +909,10 @@ static void try_to_simplify_commit(struct rev_info *revs, struct commit *commit)
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relevant_change = 1;
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else
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irrelevant_change = 1;
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if (!nth_parent)
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commit->object.flags |= PULL_MERGE;
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continue;
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}
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die("bad tree compare for commit %s", oid_to_hex(&commit->object.oid));
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@ -2269,6 +2285,8 @@ static int handle_revision_opt(struct rev_info *revs, int argc, const char **arg
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} else if (!strcmp(arg, "--full-diff")) {
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revs->diff = 1;
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revs->full_diff = 1;
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} else if (!strcmp(arg, "--show-pulls")) {
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revs->show_pulls = 1;
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} else if (!strcmp(arg, "--full-history")) {
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revs->simplify_history = 0;
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} else if (!strcmp(arg, "--relative-date")) {
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@ -3023,7 +3041,8 @@ static struct commit_list **simplify_one(struct rev_info *revs, struct commit *c
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if (!cnt ||
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(commit->object.flags & UNINTERESTING) ||
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!(commit->object.flags & TREESAME) ||
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(parent = one_relevant_parent(revs, commit->parents)) == NULL)
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(parent = one_relevant_parent(revs, commit->parents)) == NULL ||
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(revs->show_pulls && (commit->object.flags & PULL_MERGE)))
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st->simplified = commit;
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else {
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pst = locate_simplify_state(revs, parent);
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@ -3606,6 +3625,10 @@ enum commit_action get_commit_action(struct rev_info *revs, struct commit *commi
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/* drop merges unless we want parenthood */
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if (!want_ancestry(revs))
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return commit_ignore;
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if (revs->show_pulls && (commit->object.flags & PULL_MERGE))
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return commit_show;
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/*
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* If we want ancestry, then need to keep any merges
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* between relevant commits to tie together topology.
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@ -34,6 +34,9 @@
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#define SYMMETRIC_LEFT (1u<<8)
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#define PATCHSAME (1u<<9)
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#define BOTTOM (1u<<10)
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/* WARNING: This is also used as REACHABLE in commit-graph.c. */
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#define PULL_MERGE (1u<<15)
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/*
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* Indicates object was reached by traversal. i.e. not given by user on
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* command-line or stdin.
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@ -43,7 +46,7 @@
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*/
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#define NOT_USER_GIVEN (1u<<25)
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#define TRACK_LINEAR (1u<<26)
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#define ALL_REV_FLAGS (((1u<<11)-1) | NOT_USER_GIVEN | TRACK_LINEAR)
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#define ALL_REV_FLAGS (((1u<<11)-1) | NOT_USER_GIVEN | TRACK_LINEAR | PULL_MERGE)
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#define TOPO_WALK_EXPLORED (1u<<27)
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#define TOPO_WALK_INDEGREE (1u<<28)
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@ -129,6 +132,7 @@ struct rev_info {
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no_walk:2,
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remove_empty_trees:1,
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simplify_history:1,
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show_pulls:1,
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topo_order:1,
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simplify_merges:1,
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simplify_by_decoration:1,
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@ -154,4 +154,124 @@ test_expect_success '--full-diff is not affected by --parents' '
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test_cmp expected actual
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'
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#
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# Create a new history to demonstrate the value of --show-pulls
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# with respect to the subtleties of simplified history, --full-history,
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# and --simplify-merges.
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#
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# .-A---M-----C--N---O---P
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# / / \ \ \/ / /
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# I B \ R-'`-Z' /
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# \ / \/ /
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# \ / /\ /
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# `---X--' `---Y--'
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#
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# This example is explained in Documentation/rev-list-options.txt
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test_expect_success 'rebuild repo' '
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rm -rf .git * &&
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git init &&
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git switch -c main &&
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echo base >file &&
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git add file &&
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test_commit I &&
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echo A >file &&
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git add file &&
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test_commit A &&
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git switch -c branchB I &&
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echo B >file &&
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git add file &&
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test_commit B &&
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git switch main &&
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test_must_fail git merge -m "M" B &&
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echo A >file &&
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echo B >>file &&
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git add file &&
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git merge --continue &&
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note M &&
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echo C >other &&
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git add other &&
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test_commit C &&
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git switch -c branchX I &&
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echo X >file &&
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git add file &&
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test_commit X &&
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git switch -c branchR M &&
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git merge -m R -Xtheirs X &&
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note R &&
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git switch main &&
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git merge -m N R &&
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note N &&
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git switch -c branchY M &&
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echo Y >y &&
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git add y &&
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test_commit Y &&
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git switch -c branchZ C &&
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echo Z >z &&
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git add z &&
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test_commit Z &&
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git switch main &&
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git merge -m O Z &&
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note O &&
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git merge -m P Y &&
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note P
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'
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check_result 'X I' -- file
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check_result 'N R X I' --show-pulls -- file
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check_result 'P O N R X M B A I' --full-history --topo-order -- file
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check_result 'N R X M B A I' --simplify-merges --topo-order --show-pulls -- file
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check_result 'R X M B A I' --simplify-merges --topo-order -- file
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check_result 'N M A I' --first-parent -- file
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check_result 'N M A I' --first-parent --show-pulls -- file
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# --ancestry-path implies --full-history
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check_result 'P O N R M' --topo-order \
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--ancestry-path A..HEAD -- file
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check_result 'P O N R M' --topo-order \
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--show-pulls \
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--ancestry-path A..HEAD -- file
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check_result 'P O N R M' --topo-order \
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--full-history \
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--ancestry-path A..HEAD -- file
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check_result 'R M' --topo-order \
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--simplify-merges \
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--ancestry-path A..HEAD -- file
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check_result 'N R M' --topo-order \
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--simplify-merges --show-pulls \
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--ancestry-path A..HEAD -- file
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test_expect_success 'log --graph --simplify-merges --show-pulls' '
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cat >expect <<-\EOF &&
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* N
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* R
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|\
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| * X
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* | M
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||||
|\ \
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||||
| * | B
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||||
| |/
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||||
* / A
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|/
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* I
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EOF
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git log --graph --pretty="%s" \
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--simplify-merges --show-pulls \
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-- file >actual &&
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||||
test_cmp expect actual
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'
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||||
|
||||
test_done
|
||||
|
||||
Loading…
Reference in New Issue
Block a user