On Mon, 18 May 2020 at 22:22, Junio C Hamano <gitster@xxxxxxxxx> wrote:
>
> Martin Ågren <martin.agren@xxxxxxxxx> writes:
>
> > I currently have the commit message below for my patch plus your fixup.
> > ...
>
> I've queued 1, 3, 4, 5, and 6 in the meantime. Todd gave us a
> replacement for 2, which I also took.
>
> Thanks.
A long weekend offline passes and it's already a week later...
Here is my original patch 7/7 plus Stolee's fixup, with the rephrased
commit message from upthread. I've tried to test it from all angles I
can think of -- AsciiDoc/Asciidoctor, man/html, doc-diff, ... It should
be low-risk and does avoid beginning ~20 paragraphs with a literal "+"
in the rendered docs for this new option.
Martin
-- >8 --
The explanation of the `--show-pulls` option added in commit 8d049e182e
("revision: --show-pulls adds helpful merges", 2020-04-10) consists of
several paragraphs and we use "+" throughout to tie them together in one
long chain of list continuations. Only thing is, we're not in any kind
of list, so these pluses end up being rendered literally.
The preceding few paragraphs describe `--ancestry-path` and there we
*do* have a list, since we've started one with `--ancestry-path::`. In
fact, we have several such lists for all the various history-simplifying
options we're discussing earlier in this file.
Thus, we're missing a list both from a consistency point of view and
from a practical rendering standpoint.
Let's start a list for `--show-pulls` where we start actually discussing
the option, and keep the paragraphs preceding it out of that list. That
is, drop all those pluses before the new list we're adding here.
Helped-by: Derrick Stolee <stolee@xxxxxxxxx>
Signed-off-by: Martin Ågren <martin.agren@xxxxxxxxx>
---
Documentation/rev-list-options.txt | 35 ++++++++++++++++--------------
1 file changed, 19 insertions(+), 16 deletions(-)
diff --git a/Documentation/rev-list-options.txt b/Documentation/rev-list-options.txt
index 04ad7dd36e..b01b2b6773 100644
--- a/Documentation/rev-list-options.txt
+++ b/Documentation/rev-list-options.txt
@@ -581,12 +581,12 @@ option does. Applied to the 'D..M' range, it results in:
Before discussing another option, `--show-pulls`, we need to
create a new example history.
-+
+
A common problem users face when looking at simplified history is that a
commit they know changed a file somehow does not appear in the file's
simplified history. Let's demonstrate a new example and show how options
such as `--full-history` and `--simplify-merges` works in that case:
-+
+
-----------------------------------------------------------------------
.-A---M-----C--N---O---P
/ / \ \ \/ / /
@@ -595,7 +595,7 @@ such as `--full-history` and `--simplify-merges` works in that case:
\ / /\ /
`---X--' `---Y--'
-----------------------------------------------------------------------
-+
+
For this example, suppose `I` created `file.txt` which was modified by
`A`, `B`, and `X` in different ways. The single-parent commits `C`, `Z`,
and `Y` do not change `file.txt`. The merge commit `M` was created by
@@ -607,19 +607,19 @@ the contents of `file.txt` at `X`. Hence, `R` is TREESAME to `X` but not
contents of `file.txt` at `R`, so `N` is TREESAME to `R` but not `C`.
The merge commits `O` and `P` are TREESAME to their first parents, but
not to their second parents, `Z` and `Y` respectively.
-+
+
When using the default mode, `N` and `R` both have a TREESAME parent, so
those edges are walked and the others are ignored. The resulting history
graph is:
-+
+
-----------------------------------------------------------------------
I---X
-----------------------------------------------------------------------
-+
+
When using `--full-history`, Git walks every edge. This will discover
the commits `A` and `B` and the merge `M`, but also will reveal the
merge commits `O` and `P`. With parent rewriting, the resulting graph is:
-+
+
-----------------------------------------------------------------------
.-A---M--------N---O---P
/ / \ \ \/ / /
@@ -628,21 +628,21 @@ merge commits `O` and `P`. With parent rewriting, the resulting graph is:
\ / /\ /
`---X--' `------'
-----------------------------------------------------------------------
-+
+
Here, the merge commits `O` and `P` contribute extra noise, as they did
not actually contribute a change to `file.txt`. They only merged a topic
that was based on an older version of `file.txt`. This is a common
issue in repositories using a workflow where many contributors work in
parallel and merge their topic branches along a single trunk: manu
unrelated merges appear in the `--full-history` results.
-+
+
When using the `--simplify-merges` option, the commits `O` and `P`
disappear from the results. This is because the rewritten second parents
of `O` and `P` are reachable from their first parents. Those edges are
removed and then the commits look like single-parent commits that are
TREESAME to their parent. This also happens to the commit `N`, resulting
in a history view as follows:
-+
+
-----------------------------------------------------------------------
.-A---M--.
/ / \
@@ -651,18 +651,18 @@ in a history view as follows:
\ / /
`---X--'
-----------------------------------------------------------------------
-+
+
In this view, we see all of the important single-parent changes from
`A`, `B`, and `X`. We also see the carefully-resolved merge `M` and the
not-so-carefully-resolved merge `R`. This is usually enough information
to determine why the commits `A` and `B` "disappeared" from history in
the default view. However, there are a few issues with this approach.
-+
+
The first issue is performance. Unlike any previous option, the
`--simplify-merges` option requires walking the entire commit history
before returning a single result. This can make the option difficult to
use for very large repositories.
-+
+
The second issue is one of auditing. When many contributors are working
on the same repository, it is important which merge commits introduced
a change into an important branch. The problematic merge `R` above is
@@ -671,10 +671,13 @@ important branch. Instead, the merge `N` was used to merge `R` and `X`
into the important branch. This commit may have information about why
the change `X` came to override the changes from `A` and `B` in its
commit message.
+
+--show-pulls::
+ In addition to the commits shown in the default history, show
+ each merge commit that is not TREESAME to its first parent but
+ is TREESAME to a later parent.
+
-The `--show-pulls` option helps with both of these issues by adding more
-merge commits to the history results. If a merge is not TREESAME to its
-first parent but is TREESAME to a later parent, then that merge is
+When a merge commit is included by `--show-pulls`, the merge is
treated as if it "pulled" the change from another branch. When using
`--show-pulls` on this example (and no other options) the resulting
graph is:
--
2.27.0.rc0
