Re: default behaviour for `gitmerge` (no arguments)

@@ -275,9 +275,9 @@ static char *substitute_branch_name(const char **string, int *len)
 		char *ref = xstrndup(*string, *len - ret);
 		struct branch *tracking = branch_get(*ref ? ref : NULL);
 
-		free(ref);
 		if (!tracking)
 			die ("No tracking branch found for '%s'", ref);
+		free(ref);
 		if (tracking->merge && tracking->merge[0]->dst) {
 			*string = xstrdup(tracking->merge[0]->dst);
 			*len = strlen(*string);

@@ -231,6 +231,10 @@ when you run 'git-merge'.
 * The special construct '@\{-<n>\}' means the <n>th branch checked out
   before the current one.
 
+* The suffix '@{upstream}' to a ref (short form 'ref@{u}') refers to
+  the branch the ref is set to build on top of.  Missing ref defaults
+  to the current branch.
+
 * A suffix '{caret}' to a revision parameter means the first parent of
   that commit object.  '{caret}<n>' means the <n>th parent (i.e.
   'rev{caret}'

@@ -5,6 +5,7 @@
 #include "blob.h"
 #include "tree-walk.h"
 #include "refs.h"
+#include "remote.h"
 
 static int find_short_object_filename(int len, const char *name, unsigned char *sha1)
 {

@@ -238,9 +239,24 @@ static int ambiguous_path(const char *path, int len)
 	return slash;
 }
 
+static inline int tracked_suffix(const char *string, int len)
+{
+	const char *suffix[] = { "@{upstream}", "@{u}" };
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(suffix); i++) {
+		int suffix_len = strlen(suffix[i]);
+		if (len >= suffix_len && !memcmp(string + len - suffix_len,
+					suffix[i], suffix_len))
+			return suffix_len;
+	}
+	return 0;
+}
+
 /*
  * *string and *len will only be substituted, and *string returned (for
- * later free()ing) if the string passed in is of the form @{-<n>}.
+ * later free()ing) if the string passed in is of the form @{-<n>} or
+ * of the form <branch>@{upstream}.
  */
 static char *substitute_branch_name(const char **string, int *len)
 {

@@ -254,6 +270,21 @@ static char *substitute_branch_name(const char **string, int *len)
 		return (char *)*string;
 	}
 
+	ret = tracked_suffix(*string, *len);
+	if (ret) {
+		char *ref = xstrndup(*string, *len - ret);
+		struct branch *tracking = branch_get(*ref ? ref : NULL);
+
+		if (!tracking)
+			die ("No tracking branch found for '%s'", ref);
+		free(ref);
+		if (tracking->merge && tracking->merge[0]->dst) {
+			*string = xstrdup(tracking->merge[0]->dst);
+			*len = strlen(*string);
+			return (char *)*string;
+		}
+	}
+
 	return NULL;
 }
 

@@ -340,8 +371,10 @@ static int get_sha1_basic(const char *str, int len, unsigned char *sha1)
 	if (len && str[len-1] == '}') {
 		for (at = len-2; at >= 0; at--) {
 			if (str[at] == '@' && str[at+1] == '{') {
-				reflog_len = (len-1) - (at+2);
-				len = at;
+				if (!tracked_suffix(str + at, len - at)) {
+					reflog_len = (len-1) - (at+2);
+					len = at;
+				}
 				break;
 			}
 		}

@@ -0,0 +1,69 @@
+#!/bin/sh
+
+test_description='test <branch>@{upstream} syntax'
+
+. ./test-lib.sh
+
+
+test_expect_success 'setup' '
+
+	test_commit 1 &&
+	git checkout -b side &&
+	test_commit 2 &&
+	git checkout master &&
+	git clone . clone &&
+	test_commit 3 &&
+	(cd clone &&
+	 test_commit 4 &&
+	 git branch --track my-side origin/side)
+
+'
+
+full_name () {
+	(cd clone &&
+	 git rev-parse --symbolic-full-name "$@")
+}
+
+commit_subject () {
+	(cd clone &&
+	 git show -s --pretty=format:%s "$@")
+}
+
+test_expect_success '@{upstream} resolves to correct full name' '
+	test refs/remotes/origin/master = "$(full_name @{upstream})"
+'
+
+test_expect_success '@{u} resolves to correct full name' '
+	test refs/remotes/origin/master = "$(full_name @{u})"
+'
+
+test_expect_success 'my-side@{upstream} resolves to correct full name' '
+	test refs/remotes/origin/side = "$(full_name my-side@{u})"
+'
+
+test_expect_success 'my-side@{u} resolves to correct commit' '
+	git checkout side &&
+	test_commit 5 &&
+	(cd clone && git fetch) &&
+	test 2 = "$(commit_subject my-side)" &&
+	test 5 = "$(commit_subject my-side@{u})"
+'
+
+test_expect_success 'not-tracking@{u} fails' '
+	test_must_fail full_name non-tracking@{u} &&
+	(cd clone && git checkout --no-track -b non-tracking) &&
+	test_must_fail full_name non-tracking@{u}
+'
+
+test_expect_success '<branch>@{u}@{1} resolves correctly' '
+	test_commit 6 &&
+	(cd clone && git fetch) &&
+	test 5 = $(commit_subject my-side@{u}@{1})
+'
+
+test_expect_success '@{u} without specifying branch fails on a detached HEAD' '
+	git checkout HEAD^0 &&
+	test_must_fail git rev-parse @{u}
+'
+
+test_done

@@ -66,4 +66,45 @@ test_expect_success '@{u} without specifying branch fails on a detached HEAD' '
 	test_must_fail git rev-parse @{u}
 '
 
+test_expect_success 'checkout -b new my-side@{u} forks from the same' '
+(
+	cd clone &&
+	git checkout -b new my-side@{u} &&
+	git rev-parse --symbolic-full-name my-side@{u} >expect &&
+	git rev-parse --symbolic-full-name new@{u} >actual &&
+	test_cmp expect actual
+)
+'
+
+test_expect_failure 'merge my-side@{u} records the correct name' '
+(
+	sq="'\''" &&
+	cd clone || exit
+	git checkout master || exit
+	git branch -D new ;# can fail but is ok
+	git branch -t new my-side@{u} &&
+	git merge -s ours new@{u} &&
+	git show -s --pretty=format:%s >actual &&
+	echo "Merge remote branch ${sq}origin/side${sq}" >expect &&
+	test_cmp expect actual
+)
+'
+
+test_expect_failure 'branch -d other@{u}' '
+	git checkout -t -b other master &&
+	git branch -d @{u} &&
+	git for-each-ref refs/heads/master >actual &&
+	>expect &&
+	test_cmp expect actual
+'
+
+test_expect_failure 'checkout other@{u}' '
+	git branch -f master HEAD &&
+	git checkout -t -b another master &&
+	git checkout @{u} &&
+	git symbolic-ref HEAD >actual &&
+	echo refs/heads/master >expect &&
+	test_cmp expect actual
+'
+
 test_done

@@ -239,24 +239,10 @@ static int ambiguous_path(const char *path, int len)
 	return slash;
 }
 
-static inline int tracked_suffix(const char *string, int len)
-{
-	const char *suffix[] = { "@{upstream}", "@{u}" };
-	int i;
-
-	for (i = 0; i < ARRAY_SIZE(suffix); i++) {
-		int suffix_len = strlen(suffix[i]);
-		if (len >= suffix_len && !memcmp(string + len - suffix_len,
-					suffix[i], suffix_len))
-			return suffix_len;
-	}
-	return 0;
-}
-
 /*
  * *string and *len will only be substituted, and *string returned (for
- * later free()ing) if the string passed in is of the form @{-<n>} or
- * of the form <branch>@{upstream}.
+ * later free()ing) if the string passed in is a magic short-hand form
+ * to name a branch.
  */
 static char *substitute_branch_name(const char **string, int *len)
 {

@@ -270,21 +256,6 @@ static char *substitute_branch_name(const char **string, int *len)
 		return (char *)*string;
 	}
 
-	ret = tracked_suffix(*string, *len);
-	if (ret) {
-		char *ref = xstrndup(*string, *len - ret);
-		struct branch *tracking = branch_get(*ref ? ref : NULL);
-
-		if (!tracking)
-			die ("No tracking branch found for '%s'", ref);
-		free(ref);
-		if (tracking->merge && tracking->merge[0]->dst) {
-			*string = xstrdup(tracking->merge[0]->dst);
-			*len = strlen(*string);
-			return (char *)*string;
-		}
-	}
-
 	return NULL;
 }
 

@@ -354,6 +325,20 @@ int dwim_log(const char *str, int len, unsigned char *sha1, char **log)
 	return logs_found;
 }
 
+static inline int upstream_mark(const char *string, int len)
+{
+	const char *suffix[] = { "@{upstream}", "@{u}" };
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(suffix); i++) {
+		int suffix_len = strlen(suffix[i]);
+		if (suffix_len <= len
+		    && !memcmp(string, suffix[i], suffix_len))
+			return suffix_len;
+	}
+	return 0;
+}
+
 static int get_sha1_1(const char *name, int len, unsigned char *sha1);
 
 static int get_sha1_basic(const char *str, int len, unsigned char *sha1)

@@ -371,7 +356,7 @@ static int get_sha1_basic(const char *str, int len, unsigned char *sha1)
 	if (len && str[len-1] == '}') {
 		for (at = len-2; at >= 0; at--) {
 			if (str[at] == '@' && str[at+1] == '{') {
-				if (!tracked_suffix(str + at, len - at)) {
+				if (!upstream_mark(str + at, len - at)) {
 					reflog_len = (len-1) - (at+2);
 					len = at;
 				}

@@ -773,17 +758,10 @@ static int grab_nth_branch_switch(unsigned char *osha1, unsigned char *nsha1,
 }
 
 /*
- * This reads "@{-N}" syntax, finds the name of the Nth previous
- * branch we were on, and places the name of the branch in the given
- * buf and returns the number of characters parsed if successful.
- *
- * If the input is not of the accepted format, it returns a negative
- * number to signal an error.
- *
- * If the input was ok but there are not N branch switches in the
- * reflog, it returns 0.
+ * Parse @{-N} syntax, return the number of characters parsed
+ * if successful; otherwise signal an error with negative value.
  */
-int interpret_branch_name(const char *name, struct strbuf *buf)
+static int interpret_nth_prior_checkout(const char *name, struct strbuf *buf)
 {
 	long nth;
 	int i, retval;

@@ -828,6 +806,60 @@ release_return:
 }
 
 /*
+ * This reads short-hand syntax that not only evaluates to a commit
+ * object name, but also can act as if the end user spelled the name
+ * of the branch from the command line.
+ *
+ * - "@{-N}" finds the name of the Nth previous branch we were on, and
+ *   places the name of the branch in the given buf and returns the
+ *   number of characters parsed if successful.
+ *
+ * - "<branch>@{upstream}" finds the name of the other ref that
+ *   <branch> is configured to merge with (missing <branch> defaults
+ *   to the current branch), and places the name of the branch in the
+ *   given buf and returns the number of characters parsed if
+ *   successful.
+ *
+ * If the input is not of the accepted format, it returns a negative
+ * number to signal an error.
+ *
+ * If the input was ok but there are not N branch switches in the
+ * reflog, it returns 0.
+ */
+int interpret_branch_name(const char *name, struct strbuf *buf)
+{
+	char *cp;
+	struct branch *upstream;
+	int namelen = strlen(name);
+	int len = interpret_nth_prior_checkout(name, buf);
+	int tmp_len;
+
+	if (!len)
+		return len; /* syntax Ok, not enough switches */
+	if (0 < len)
+		return len; /* consumed from the front */
+	cp = strchr(name, '@');
+	if (!cp)
+		return -1;
+	tmp_len = upstream_mark(cp, namelen - (cp - name));
+	if (!tmp_len)
+		return -1;
+	len = cp + tmp_len - name;
+	cp = xstrndup(name, cp - name);
+	upstream = branch_get(*cp ? cp : NULL);
+	if (!upstream
+	    || !upstream->merge
+	    || !upstream->merge[0]->dst)
+		return error("No upstream branch found for '%s'", cp);
+	free(cp);
+	cp = shorten_unambiguous_ref(upstream->merge[0]->dst, 0);
+	strbuf_reset(buf);
+	strbuf_addstr(buf, cp);
+	free(cp);
+	return len;
+}
+
+/*
  * This is like "get_sha1_basic()", except it allows "sha1 expressions",
  * notably "xyz^" for "parent of xyz"
  */

@@ -76,7 +76,7 @@ test_expect_success 'checkout -b new my-side@{u} forks from the same' '
 )
 '
 
-test_expect_failure 'merge my-side@{u} records the correct name' '
+test_expect_success 'merge my-side@{u} records the correct name' '
 (
 	sq="'\''" &&
 	cd clone || exit

@@ -90,7 +90,7 @@ test_expect_failure 'merge my-side@{u} records the correct name' '
 )
 '
 
-test_expect_failure 'branch -d other@{u}' '
+test_expect_success 'branch -d other@{u}' '
 	git checkout -t -b other master &&
 	git branch -d @{u} &&
 	git for-each-ref refs/heads/master >actual &&

@@ -98,7 +98,7 @@ test_expect_failure 'branch -d other@{u}' '
 	test_cmp expect actual
 '
 
-test_expect_failure 'checkout other@{u}' '
+test_expect_success 'checkout other@{u}' '
 	git branch -f master HEAD &&
 	git checkout -t -b another master &&
 	git checkout @{u} &&

@@ -0,0 +1,41 @@
+#!/bin/sh
+
+test_description='various @{whatever} syntax tests'
+. ./test-lib.sh
+
+test_expect_success 'setup' '
+	test_commit one &&
+	test_commit two
+'
+
+check_at() {
+	echo "$2" >expect &&
+	git log -1 --format=%s "$1" >actual &&
+	test_cmp expect actual
+}
+
+test_expect_success '@{0} shows current' '
+	check_at @{0} two
+'
+
+test_expect_success '@{1} shows old' '
+	check_at @{1} one
+'
+
+test_expect_success '@{now} shows current' '
+	check_at @{now} two
+'
+
+test_expect_success '@{30.years.ago} shows old' '
+	check_at @{30.years.ago} one
+'
+
+test_expect_success 'silly approxidates work' '
+	check_at @{3.hot.dogs.and.30.years.ago} one
+'
+
+test_expect_failure 'complain about total nonsense' '
+	test_must_fail git log -1 --format=%s @{utter.bogosity}
+'
+
+test_done

@@ -107,4 +107,18 @@ test_expect_success 'checkout other@{u}' '
 	test_cmp expect actual
 '
 
+cat >expect <<EOF
+commit 8f489d01d0cc65c3b0f09504ec50b5ed02a70bd5
+Reflog: refs/heads/master@{0} (C O Mitter <committer@example.com>)
+Reflog message: branch: Created from HEAD
+Author: A U Thor <author@example.com>
+Date:   Thu Apr 7 15:15:13 2005 -0700
+
+    3
+EOF
+test_expect_failure 'log -g other@{u}' '
+	git log -1 -g other@{u} >actual &&
+	test_cmp expect actual
+'
+
 test_done