Add configuration for git

- Add .config/git/config
  + Define aliases
  + Configure default behavior in various situations
  + Add user information with signing key
- Add .config/git/commit_msg_template.txt
- Add .config/git/ignore
- Integrate `git` aliases into the shell

.local/bin/git-aliases

@@ -0,0 +1,35 @@
+#!/bin/sh
+
+# List the names of all `git` aliases, one per line
+#
+# With the "--real" flag, only the "real" aliases are listed,
+# which are those with less than 7 characters in their name
+# as defined under "[alias]" in ~/.config/git/config
+#
+# Usage: git aliases [--real]
+
+set -eu
+
+
+_max_length=999
+
+
+for arg in "$@"; do
+
+    case "$arg" in
+        --real)
+            _max_length=7
+            ;;
+        *)
+            echo 'Usage: git aliases [--real]' >&2
+            exit 2
+            ;;
+    esac
+
+done
+
+
+
+git --list-cmds=alias \
+    | awk -v max="$_max_length" 'length($0) < max' \
+    | sort

.local/bin/git-aliases-n-sub-commands

@@ -0,0 +1,15 @@
+#!/bin/sh
+
+# List the names of all `git` aliases and custom sub-commands, one per line
+#
+# Usage: git aliases-n-sub-commands
+
+set -eu
+
+
+{
+
+    git --list-cmds=alias
+    git --list-cmds=others
+
+} | sort -u

.local/bin/git-cat-all

@@ -0,0 +1,93 @@
+#!/bin/sh
+
+# Print the contents of all tracked text files to stdout,
+# each preceded by a header with its filename
+#
+# With "-a", binary files are included as well
+#
+# With "-m", only files with unstaged modifications are printed
+#
+# With "-n", the headers are omitted
+#
+# Usage: git cat-all [-a] [-m] [-n] [<pathspec> ...]
+
+set -eu
+
+
+
+# Error if we are not in a `git` repository
+git rev-parse --git-dir >/dev/null
+
+# Without any commit, there is nothing to print reliably
+git rev-parse --verify --quiet HEAD >/dev/null || {
+    echo "fatal: no commits yet" >&2
+    exit 1
+}
+
+
+
+_textonly=yes
+_lsflags=
+_cmd='printf "\n\n===== %s =====\n\n" "{}"; cat "{}"'
+_headers=yes
+
+
+while [ $# -gt 0 ]; do
+    case $1 in
+        -a) _textonly=no
+            shift
+            ;;
+        -m) _lsflags=-m
+            shift
+            ;;
+        -n) _cmd='printf "\n\n"; cat "{}"'
+            _headers=no
+            shift
+            ;;
+        --) shift
+            break
+            ;;
+        -*) echo "Usage: git cat-all [-a] [-m] [-n] [<pathspec> ...]" >&2
+            exit 2
+            ;;
+        *)  break
+            ;;
+    esac
+done
+
+
+
+# Because `git` runs scripts on the `$PATH` in the current directory
+cd "$(git rev-parse --show-toplevel)"
+
+
+# An empty file counts as text
+# => `grep` alone would misjudge it
+#    because it never matches in a file without any lines
+if [ "$_textonly" = "yes" ]; then
+    _cmd='if [ ! -s "{}" ] || grep -Iq "" "{}"; then '"$_cmd"'; fi'
+fi
+
+
+# `git ls-files -m` also lists files deleted from the working tree
+# => Skip them because `cat` would fail
+if [ -n "$_lsflags" ]; then
+    _cmd='if [ -f "{}" ]; then '"$_cmd"'; fi'
+fi
+
+
+
+if [ "$_headers" = "yes" ]; then
+    printf "Repository: %s\n" "$(basename "$PWD")"
+    printf "Branch: %s @ %s\n" \
+        "$(git rev-parse --abbrev-ref HEAD)" \
+        "$(git rev-parse --short HEAD)"
+fi
+
+
+
+git ls-files \
+    -z $_lsflags \
+    -- \
+    "$@" \
+    | xargs -0 -I{} sh -c "$_cmd"

.local/bin/git-checkout-dev

@@ -0,0 +1,8 @@
+#!/bin/sh
+
+# Check out the "develop" branch, whatever it is called
+
+set -eu
+
+
+exec git checkout-first-existing-branch dev develop development

.local/bin/git-checkout-first-existing-branch

@@ -0,0 +1,28 @@
+#!/bin/sh
+
+# Check out the first of the given branches that exists,
+# looking at both local branches and the ones on `origin`
+#
+# Usage: git checkout-first-existing-branch <branch> [<branch> ...]
+
+set -eu
+
+
+if [ $# -eq 0 ]; then
+    echo "Usage: git checkout-first-existing-branch <branch> [<branch> ...]" >&2
+    exit 2
+fi
+
+
+for _branch in "$@"; do
+
+    if git show-ref --verify --quiet "refs/heads/$_branch" \
+    || git show-ref --verify --quiet "refs/remotes/origin/$_branch"; then
+        exec git checkout "$_branch"
+    fi
+
+done
+
+
+echo "None of these branches exists: $*" >&2
+exit 1

.local/bin/git-checkout-main

@@ -0,0 +1,8 @@
+#!/bin/sh
+
+# Check out the "main" branch, whatever it is called
+
+set -eu
+
+
+exec git checkout-first-existing-branch main master

.local/bin/git-clean-all

@@ -0,0 +1,54 @@
+#!/bin/sh
+
+# Reset the working directory to `HEAD` and remove everything not tracked,
+# except the files listed in $KEEP in ~/.local/bin/git-clean-ignored
+#
+# This is irreversible, so the changes are shown first and confirmed,
+# unless "--force" is passed
+#
+# Usage: git clean-all [--force]
+
+set -eu
+
+
+# `git` runs scripts on the `$PATH` in the current directory,
+# whereas it runs "!" aliases at the top level of the repository
+cd "$(git rev-parse --show-toplevel)"
+
+
+case "${1:-}" in
+    --force) _forced=1 ;;
+         "") _forced=0 ;;
+          *) echo "Usage: git clean-all [--force]" >&2; exit 2 ;;
+esac
+
+
+if [ "$_forced" -ne 1 ]; then
+
+    echo "Tracked files to be reset to HEAD:"
+    git diff --stat HEAD || true
+    echo ""
+
+    echo "Untracked and ignored files to be removed:"
+    # Keep the "-e" flags in sync with the other two copies:
+    #  - the "-e" flags of `clean-untracked` in ~/.config/git/config
+    #  - `$KEEP` in ~/.local/bin/git-clean-ignored
+    git clean -x -d -n -e ".python-version" -e ".env"
+    echo ""
+
+    printf "This CANNOT be undone. Continue? [y/N] "
+    read -r _answer || _answer=""
+
+    case "$_answer" in
+        [yY] | [yY][eE][sS]) ;;
+        *) echo "Aborted" >&2; exit 1 ;;
+    esac
+
+fi
+
+
+git reset --hard
+
+git clean-ignored
+
+git clean-untracked

.local/bin/git-clean-ignored

@@ -0,0 +1,46 @@
+#!/bin/sh
+
+# Remove all files ignored by `git`, except the ones listed in $KEEP below
+#
+# `git clean` does not accept "-e" together with "-X",
+# so the files to be kept are moved aside and then restored
+#
+# Usage: git clean-ignored [<git clean options>]
+
+set -eu
+
+
+# Keep this list in sync with the other two copies:
+#  - the "-e" flags of `clean-untracked` in ~/.config/git/config
+#  - the preview in ~/.local/bin/git-clean-all
+KEEP=".env .python-version"
+
+SUFFIX=".git-clean-ignored.bak"
+
+
+# `git` runs scripts on the `$PATH` in the current directory,
+# whereas it runs "!" aliases at the top level of the repository
+cd "$(git rev-parse --show-toplevel)"
+
+
+_restore() {
+    for _file in $KEEP; do
+        if [ -f "$_file$SUFFIX" ]; then
+            mv "$_file$SUFFIX" "$_file"
+        fi
+    done
+}
+
+
+# Restore the kept files even if `git clean` fails or the user aborts
+trap _restore EXIT HUP INT TERM
+
+
+for _file in $KEEP; do
+    if [ -f "$_file" ]; then
+        mv "$_file" "$_file$SUFFIX"
+    fi
+done
+
+
+git clean -X -d -f "$@"

.local/bin/git-ff-all

@@ -0,0 +1,32 @@
+#!/bin/sh
+
+# Fast-forward all local branches that track a remote branch
+#
+# Branches with local-only commits are skipped
+#
+# Usage: git ff-all
+
+set -eu
+
+
+git fetch --all --prune
+
+
+current="$(git branch --show-current)"
+
+
+git for-each-ref --format='%(refname:short) %(upstream:short)' refs/heads/ |
+while read -r branch upstream; do
+
+    [ -n "$upstream" ] || continue
+
+    if [ "$branch" = "$current" ]; then
+        git merge --ff-only "$upstream" 2>/dev/null \
+            || echo "Skipped $branch (not a fast forward)"
+        continue
+    fi
+
+    git fetch . "$upstream:$branch" 2>/dev/null \
+        || echo "Skipped $branch (not a fast forward)"
+
+done

.local/bin/git-gc-everything

@@ -0,0 +1,18 @@
+#!/bin/sh
+
+# Delete EVERYTHING not reachable from a branch from the repository
+#
+# This expires the reflog as well!
+#
+# Usage: git gc-everything [<git gc options>]
+
+set -eu
+
+
+exec git \
+    -c gc.pruneExpire=now \
+    -c gc.reflogExpire=0 \
+    -c gc.reflogExpireUnreachable=0 \
+    -c gc.rerereresolved=0 \
+    -c gc.rerereunresolved=0 \
+    gc "$@"

.local/bin/git-match-remote

@@ -0,0 +1,35 @@
+#!/bin/sh
+
+# Make all local branches match the remote branch they track,
+# discarding local-only commits and, on the current branch,
+# uncommitted changes as well
+#
+# Branches without an upstream are left alone
+#
+# Usage: git match-remote
+
+set -eu
+
+
+git fetch --all --prune
+
+
+current="$(git branch --show-current)"
+
+
+git for-each-ref --format='%(refname:short) %(upstream:short)' refs/heads/ |
+while read -r branch upstream; do
+
+    [ -n "$upstream" ] || continue
+
+    git rev-parse --verify --quiet "$upstream" >/dev/null || continue
+
+    if [ "$branch" = "$current" ]; then
+        git reset --hard "$upstream"
+        continue
+    fi
+
+    git branch -f "$branch" "$upstream"
+    echo "Moved $branch to $upstream"
+
+done

.local/bin/git-point-branch-at

@@ -0,0 +1,21 @@
+#!/bin/sh
+
+# Move a branch to a commit, whether or not it is checked out
+#
+# Usage: git point-branch-at [<branch>] <commit>
+
+set -eu
+
+
+case $# in
+    1) _branch=$(git rev-parse --abbrev-ref HEAD); _commit=$1 ;;
+    2) _branch=$1; _commit=$2 ;;
+    *) echo "Usage: git point-branch-at [<branch>] <commit>" >&2; exit 2 ;;
+esac
+
+
+if [ "$_branch" = "$(git rev-parse --abbrev-ref HEAD)" ]; then
+    exec git reset --keep "$_commit"
+else
+    exec git branch --force "$_branch" "$_commit"
+fi

.local/bin/git-prune-delete

@@ -0,0 +1,23 @@
+#!/bin/sh
+
+# Delete the local branches whose upstream branch was deleted on the remote
+#
+# `git branch --delete` without "--force" is used,
+# so branches holding unmerged commits are kept
+#
+# Usage: git prune-delete
+
+set -eu
+
+
+_branches=$(git prune-show)
+
+
+if [ -z "$_branches" ]; then
+    echo "No branches to prune"
+    exit 0
+fi
+
+
+# shellcheck disable=SC2086  # because branch names never contain whitespace
+git branch --delete $_branches

.local/bin/git-prune-show

@@ -0,0 +1,15 @@
+#!/bin/sh
+
+# Show the local branches whose upstream branch was deleted on the remote
+#
+# Usage: git prune-show
+
+set -eu
+
+
+git fetch --prune
+
+git branch \
+    --format='%(refname:short) %(upstream:track)' \
+    --list \
+    | awk '$2 == "[gone]" { print $1 }'