autogen.sh now configures git only on request

* autogen.sh (do_autoconf, do_git): New vars.
Support new arguments --help, all, autoconf, git.
By default, just do autoconf-related configuration, not git.
Prefer 'echo' to 'cat <<EOF ...', as this tends to avoid temp files.
If GNU cp is available, use it to backup .git/config before
changing it.  When configuring git, chatter about what is being
done, and configure git to check hashes.  Avoid some duplicate
file name specification when creating git hooks.

* GNUmakefile (ALL_IF_GIT): New macro.
(configure): Use it.
* INSTALL.REPO: Suggest './autogen.sh all'.

3 files changed, 124 insertions, 60 deletions

diff --git a/GNUmakefile b/GNUmakefile
index 83bb718a960..e6941b03b30 100644
--- a/GNUmakefile
+++ b/GNUmakefile
@@ -62,10 +62,13 @@ default $(ORDINARY_GOALS): Makefile
 # Execute in sequence, so that multiple user goals don't conflict.
 .NOTPARALLEL:
 
+# 'all' if a .git subdirectory is present, empty otherwise.
+ALL_IF_GIT = $(subst .git,all,$(wildcard .git))
+
 configure:
         @echo >&2 'There seems to be no "configure" file in this directory.'
-        @echo >&2 'Running ./autogen.sh ...'
-        ./autogen.sh
+        @echo >&2 Running ./autogen.sh $(ALL_IF_GIT) ...
+        ./autogen.sh $(ALL_IF_GIT)
         @echo >&2 '"configure" file built.'
 
 Makefile: configure
diff --git a/INSTALL.REPO b/INSTALL.REPO
index 1720758928c..7497f1f2969 100644
--- a/INSTALL.REPO
+++ b/INSTALL.REPO
@@ -18,9 +18,10 @@ makeinfo  - not strictly necessary, but highly recommended, so that
   you can build the manuals.
 
 To use the autotools, run the following shell command to generate the
-'configure' script and some related files:
+'configure' script and some related files, and to set up your git
+configuration:
 
-  $ ./autogen.sh
+  $ ./autogen.sh all
 
 You can then configure your build as follows:
 
diff --git a/autogen.sh b/autogen.sh
index a63c53c903c..2ed58e15aea 100755
--- a/autogen.sh
+++ b/autogen.sh
@@ -103,16 +103,35 @@ check_version ()
     return 2
 }
 
+do_autoconf=false
+do_git=false
+
+for arg in ${*-autoconf}; do
+    case $arg in
+      --help)
+        exec echo "$0: usage: $0 [all|autoconf|git]";;
+      all)
+        do_autoconf=true do_git=true;;
+      autoconf)
+        do_autoconf=true;;
+      git)
+        do_git=true;;
+      *)
+        echo >&2 "$0: $arg: unknown argument"; exit 1;;
+    esac
+done
+
+
+# Generate Autoconf and Automake related files, if requested.
 
-cat <<EOF
-Checking whether you have the necessary tools...
-(Read INSTALL.REPO for more details on building Emacs)
+if $do_autoconf; then
 
-EOF
+  echo 'Checking whether you have the necessary tools...
+(Read INSTALL.REPO for more details on building Emacs)'
 
-missing=
+  missing=
 
-for prog in $progs; do
+  for prog in $progs; do
 
     sprog=`echo "$prog" | sed 's/-/_/g'`
 
@@ -138,15 +157,13 @@ for prog in $progs; do
         eval ${sprog}_why=\""$stat"\"
     fi
 
-done
-
+  done
 
-if [ x"$missing" != x ]; then
 
-    cat <<EOF
+  if [ x"$missing" != x ]; then
 
-Building Emacs from the repository requires the following specialized programs:
-EOF
+    echo '
+Building Emacs from the repository requires the following specialized programs:'
 
     for prog in $progs; do
         sprog=`echo "$prog" | sed 's/-/_/g'`
@@ -157,10 +174,8 @@ EOF
     done
 
 
-    cat <<EOF
-
-Your system seems to be missing the following tool(s):
-EOF
+    echo '
+Your system seems to be missing the following tool(s):'
 
     for prog in $missing; do
         sprog=`echo "$prog" | sed 's/-/_/g'`
@@ -170,8 +185,7 @@ EOF
         echo "$prog ($why)"
     done
 
-    cat <<EOF
-
+    echo '
 If you think you have the required tools, please add them to your PATH
 and re-run this script.
 
@@ -198,65 +212,102 @@ autoreconf -fi -I m4
 
 instead of this script.
 
-Please report any problems with this script to bug-gnu-emacs@gnu.org .
-EOF
+Please report any problems with this script to bug-gnu-emacs@gnu.org .'
 
     exit 1
+  fi
+
+  echo 'Your system has the required tools.'
+  echo "Running 'autoreconf -fi -I m4' ..."
+
+
+  ## Let autoreconf figure out what, if anything, needs doing.
+  ## Use autoreconf's -f option in case autoreconf itself has changed.
+  autoreconf -fi -I m4 || exit $?
+
+  ## Create a timestamp, so that './autogen.sh; make' doesn't
+  ## cause 'make' to needlessly run 'autoheader'.
+  echo timestamp > src/stamp-h.in || exit
 fi
 
-echo 'Your system has the required tools.'
-echo "Running 'autoreconf -fi -I m4' ..."
 
+# True if the Git setup was OK before autogen.sh was run.
 
-## Let autoreconf figure out what, if anything, needs doing.
-## Use autoreconf's -f option in case autoreconf itself has changed.
-autoreconf -fi -I m4 || exit $?
+git_was_ok=true
 
-## Create a timestamp, so that './autogen.sh; make' doesn't
-## cause 'make' to needlessly run 'autoheader'.
-echo timestamp > src/stamp-h.in || exit
+if $do_git; then
+    case `cp --help 2>/dev/null` in
+      *--backup*--verbose*)
+        cp_options='--backup=numbered --verbose';;
+      *)
+        cp_options='-f';;
+    esac
+fi
 
 
-## Configure Git, if using Git.
-if test -d .git && (git status -s) >/dev/null 2>&1; then
+# Like 'git config NAME VALUE' but verbose on change and exiting on failure.
+# Also, do not configure unless requested.
 
-    # Configure 'git diff' hunk header format.
+git_config ()
+{
+    name=$1
+    value=$2
+
+    ovalue=`git config --get "$name"` && test "$ovalue" = "$value" || {
+        if $do_git; then
+            if $git_was_ok; then
+                echo 'Configuring local git repository...'
+                case $cp_options in
+                  --backup=*)
+                    cp $cp_options --force .git/config .git/config || exit;;
+                esac
+            fi
+            echo "git config $name '$value'"
+            git config "$name" "$value" || exit
+        fi
+        git_was_ok=false
+    }
+}
+
+## Configure Git, if requested.
+
+# Check hashes when transferring objects among repositories.
+
+git_config transfer.fsckObjects true
+
+
+# Configure 'git diff' hunk header format.
 
-    git config 'diff.elisp.xfuncname' \
-        '^\(def[^[:space:]]+[[:space:]]+([^()[:space:]]+)' || exit
-    git config 'diff.texinfo.xfuncname' \
-        '^@node[[:space:]]+([^,[:space:]][^,]+)' || exit
+git_config diff.elisp.xfuncname \
+           '^\(def[^[:space:]]+[[:space:]]+([^()[:space:]]+)'
+git_config diff.texinfo.xfuncname \
+           '^@node[[:space:]]+([^,[:space:]][^,]+)'
 
 
-    # Install Git hooks.
+# Install Git hooks.
 
-    tailored_hooks=
-    sample_hooks=
+tailored_hooks=
+sample_hooks=
 
-    for hook in commit-msg pre-commit; do
-        cmp build-aux/git-hooks/$hook .git/hooks/$hook >/dev/null 2>&1 ||
+for hook in commit-msg pre-commit; do
+    cmp build-aux/git-hooks/$hook .git/hooks/$hook >/dev/null 2>&1 ||
         tailored_hooks="$tailored_hooks $hook"
-    done
-    for hook in applypatch-msg pre-applypatch; do
-        test ! -r .git/hooks/$hook.sample ||
-        cmp .git/hooks/$hook.sample .git/hooks/$hook >/dev/null 2>&1 ||
+done
+for hook in applypatch-msg pre-applypatch; do
+    src=.git/hooks/$hook.sample
+    cmp "$src" .git/hooks/$hook >/dev/null 2>&1 ||
         sample_hooks="$sample_hooks $hook"
-    done
+done
 
-    if test -n "$tailored_hooks$sample_hooks"; then
+if test -n "$tailored_hooks$sample_hooks"; then
+    if $do_git; then
         echo "Installing git hooks..."
 
-        case `cp --help 2>/dev/null` in
-          *--backup*--verbose*)
-            cp_options='--backup=numbered --verbose';;
-          *)
-            cp_options='-f';;
-        esac
-
         if test -n "$tailored_hooks"; then
             for hook in $tailored_hooks; do
-                cp $cp_options build-aux/git-hooks/$hook .git/hooks || exit
-                chmod a-w .git/hooks/$hook || exit
+                dst=.git/hooks/$hook
+                cp $cp_options build-aux/git-hooks/$hook "$dst" || exit
+                chmod a-w "$dst" || exit
             done
         fi
 
@@ -266,10 +317,19 @@ if test -d .git && (git status -s) >/dev/null 2>&1; then
                 chmod a-w .git/hooks/$hook || exit
             done
         fi
+    else
+        git_was_ok=false
     fi
 fi
 
-echo "You can now run './configure'."
+if test ! -f configure; then
+    echo "You can now run '$0 autoconf'."
+elif test -d .git && test $git_was_ok = false && test $do_git = false; then
+    echo "You can now run '$0 git'."
+elif test ! -f config.status ||
+        test -n "`find src/stamp-h.in -newer config.status`"; then
+    echo "You can now run './configure'."
+fi
 
 exit 0