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--- git_merge [2019/03/06 15:22] – [Squashing] rpjday
+++ git_merge [2019/03/13 13:09] (current) – [Global merge.ff option] rpjday
@@ Line 66: / Line 66: @@
              /          master
         D---E
+</code>
+or, depicted another way:
+<code>
+        D---E---A---B---C master
+                          topic
 </code>
@@ Line 231: / Line 238: @@
 ==== Fast-forwarding ====
+Recall a fast-forward merge:
+<code>
+              A---B---C topic
+             /          master
+        D---E
+</code>
+You may or may not want that:
 <code>
@@ Line 302: / Line 319: @@
 </code>
-===== Setting branch options =====
+===== Setting merge options =====
-You can set per-branch merge options as explained [[https://stackoverflow.com/questions/37352976/how-to-make-squash-default-on-a-merge|here]]:
+==== Per-branch merge options ====
+From ''man git-config'', you can set (either locally or globally) //per-branch// merge options:
 <code>
-$ git config --global branch.master.mergeOptions "--squash"
+branch.<name>.mergeOptions
+    Sets default options for merging into branch <name>. The
+    syntax and supported options are the same as those of git-
+    merge(1), but option values containing whitespace
+    characters are currently not supported.
+</code>
+For example, if you wanted to prevent any fast-forward merges to any ''master'' branch across all of your repositories, you could:
+<code>
+$ git config --global branch.master.mergeOptions "--no-ff"
+</code>
+==== Global merge.ff option ====
+For merging, there is at least one repo-wide merge option you can set (see ''man git-merge''):
+<code>
+merge.ff
+    By default, Git does not create an extra merge commit when
+    merging a commit that is a descendant of the current
+    commit. Instead, the tip of the current branch is
+    fast-forwarded. When set to false, this variable tells Git
+    to create an extra merge commit in such a case (equivalent
+    to giving the --no-ff option from the command line). When
+    set to only, only such fast-forward merges are allowed
+    (equivalent to giving the --ff-only option from the command
+    line).
+</code>
+So for widespread fast-forward merge configuration:
+<code>
+$ git config --global merge.ff "true"
+</code>
+This setting is superseded by any per-branch fast-forward merge setting.
+===== Merge strategies =====
+==== ours ====
+Technically record a merge while totally ignoring its content -- for record-keeping.
+Example:
+<code>
+$ git checkout master
+$ git merge --strategy=ours <obsolete branch>
+</code>
+How to make ''master'' look exactly like ''develop'':
+<code>
+$ git checkout topic
+$ git merge -s ours master
+$ git checkout master
+$ git merge --ff-only topic
+</code>
+To do this for an arbitrary commit, create a temporary branch:
+<code>
+$ git checkout -b tempbranch <commit ID>
+$ git merge -s ours master
+$ git checkout master
+$ git merge --ff-only tempbranch
 </code>