Differences

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--- git [2026/06/07 04:14] – [log] jhagstrand
+++ git [2026/06/16 00:13] (current) – [diff] jhagstrand
@@ Line 29: / Line 29: @@
   * HEAD - ?
   * detached head - ?
+  * tree-ish ?
   * commit-ish
   * SHA-1 value
@@ Line 184: / Line 185: @@
 in the the meantime, to bring master changes into the feature, do a rebase,
-	handle the conflicts now, so the future feature merge will run without conflicts
+  * handle the conflicts now, so the future feature merge will run without conflicts
+  * handle conflicts conflicts in the feature branch, not when attempting the final feature merge
-handle conflicts conflicts in the feature branch, not when attempting the final feature merge
+==== Merge ====
+  # merge a feature branch back into the master branch
+  git checkout master
+  git merge feature
+That simple command "git merge feature" operates in three different ways.
+First it checks whether any changes have been made to the master branch. And if so, it checks whether there are conflicts with changes made to the feature branch.
+ - No changes made on master branch.  The merge will execute a **fast-forward**.  No actual merge is necessary.  Git just moves the master pointer to the top of the feature branch.
+ - Changes have been made on the master, but no conflicts. Now we are in a merge situation. Instead of doing a fast forward, it merges the updated files as necessary and then automatically commits those updated files.  That is called the merge commit. All of the commits made in the branch stay in the log but in a loop.
+ - Changes have been made on the master, and there are conflicts.  That means changes were made to the same lines in the same file in both the master and the feature branch.  Human decision-making is required here.  The merge stops.  The human resolves the conflicts, executes git merge --resume, and then does the merge commit manually.
+Starting situation\\
+There are commits on the feature branch.\\
+What about the master branch?  There are three possibilities:
+  * no commits on the master
+  * commits on the master but no conflicts
+  * commits on the master with conflicts
+Desired outcome.\\
+The master branch is up-to-date, and the feature branch is gone.\\
+But how will the log look?  There are three possibilities:
+  * Linear. The feature branch commits are all present in the master branch, as if the branch never existed.
+  * Indented. The feature branch commits have are all present, but indented under a merge commit, so you can see there must have been a branch there at one time.
+  * Collapsed. The feature branch commits are all gone, replaced by a single merge commit with a hand-written merge message that summarizes all the commits of the branch.
+==== Squash Merge ====
+The --squash option, the merge command does not really do a merge.  Instead it copies all of the changed files from the feature branch to the master branch.  So now you do a single commit on the master branch, write a commit message summarizing all the individual commits made on the feature branch.
+This is one of the ways to collapse a developer's many chaotic commits into a single nice-looking well-thought-out commit.
+  # Make sure you're on the branch you want to merge into
+  git checkout master
+  # merge the feature branch with --squash option
+  # this stages all the file changes into the master branch
+  git merge --squash feature
+  # ask for status now and you'll see all the changes ready for commit
+  git status
+  # now commit
+  git commit -m "feat: add feature command"
+  # delete the feature branch
+  git branch -D feature
+  # for fun do a log all between these commands to see what's going on
+  git log --all --oneline -15 --graph --decorate
+==== Log ====
+git commit adds an entry to the log.
+How to fuck with the log.
+  * git merge
+  * git rebase
+  * git reset
+git reset --hard HEAD^
+Effectively deletes the most recent commit.  Equivalent to aider /undo.
@@ Line 203: / Line 273: @@
 ====diff====
-Use diff to find the differences between two branches or between two files.\\
+Use diff to find the differences between two commits.\\
-Note that there is a big difference between .. and ... between the two commit designations.\\
-Also the two hyphens -- can go before or after the filename and that alters the output.\\
-  git diff master...featurebranch  # compare two branches
+  git diff 1bde095 b0ba90d   # compare two commits
+  git diff master sidebar    # compare two branches
-  git diff 1bde095..b0ba90d -- html/js/hud.js  # compare two different commits of a file
+  git diff master sidebar hud.js  # compare two versions of a file
 By default diff compares all of the currently modified files.
@@ Line 219: / Line 287: @@
 Additional options.
+  git diff master sidebar --stat   # show filenames and counts only
   git diff -U0	# do not display context
-  git diff -w	# ignore whitespace
-  git diff -w --word-diff-regex=[^[:space:]]	# ignore whitespace additional
+Whitespace.\\
 In .gitconfig, add
 [core] whitespace = -trailing-space,-indent-with-non-tab,-tab-in-indent
+  git diff -w	# ignore whitespace
+  git diff -w --word-diff-regex=[^[:space:]]	# ignore whitespace additional
-====log====
+Dots.\\
+If both master and sidebar have changed, and you want to see only differences in sidebar, use three dots.  (This is a shortcut to naming the commit specifically.)\\
+Warning! Two dots vs three dots makes a difference, and the difference is reversed in git diff vs git log.\\
-git log
+  git diff master sidebar poker.js  # compare changes from latest master to latest sidebar
+  git diff master..sidebar poker.js  # same as no dots
+  git diff master...sidebar poker.js  # not latest master but master when sidebar branched
-git log --oneline -10
+Double hyphens.\\
+I don't know why this is used.\\
-git log --oneline --graph # shows a hierarchy of branches
+  git diff master sidebar hud.js
+  git diff master sidebar -- hud.js
+  git diff master sidebar hud.js --
+====log====
+  git log
+  git log master   # show log for one branch
+  git log --oneline -10  # default to currently checked out branch
+  git log --all --oneline --graph --decorate  # all branches, graph hierarchy
+  git log --oneline -10     # topmost n lines
+  git log --all --pretty=fuller
 ==== interactive rebase ====
@@ Line 250: / Line 334: @@
 A note about reordering the commits.  The interactive rebase operation will start at the base and reapply your commits in new new order, rewriting your source code files in each commit.  It is possible to break code if you make a mistake.
+https://www.sitepoint.com/git-interactive-rebase-guide/
 ===== How to use =====
+==== Configuration ====
+Use git config --global to set name and email.
+  * Support anonymity by using a shielded email, like for example the private GitLab noreply masked email.
+  * Consider using a pair-programming persona as user.name to give credit to the AI author.
+  $ git config --global user.name "Your Name"
+  $ git config --global user.name "Your Name & Gemini 1.5 Flash"  # pair-programming personna
+  $ git config --global user.email "jerry@gmail.com"              # protect privacy on public host like gitlab
+Aider automatically adds a Co-authored by: line to the body.  Tell aider to skip that by adding parameters to .aider.conf.yml file:
+  attribute-author: false
+  attribute-committer: false
 ====Create a new repository====